Porous acrylic synthetic fibers comprising cellulose acetate in an acrylic matrix

ABSTRACT

Porous acrylic synthetic fibers having water absorption property and having substantially no microvoids but having mainly macrovoids are produced by spinning an organic solvent solution containing 15˜35% by weight of a polymer consisting of 2˜30 parts by weight of cellulose acetate and 70˜98 parts by weight of an acrylic polymer into a coagulation bath at a temperature of no higher than 30° C., primarily drawing the spun fibers at a draw ratio of 2.5˜8.0 times to form water swelled fibers wherein macrovoids are distributed, drying the water swelled fibers at a temperature of 100˜180° C. to a water content of no greater than 1.0% by weight and secondarily drawing the dried fibers under wet heat to elongate the macrovoid structure. 
     This invention includes acrylic composite fibers having the water absorption property, wherein at least one of components A and B consisting of 2˜50% by weight of cellulose acetate and 50˜98% by weight of an acrylic polymer and another component B consisting of an acrylic polymer are bonded in a conjugate ratio of 2/8˜8/2 (by weight) along the fiber axial direction, one component A having substantially no microvoids but having mainly macrovoids, and a method for producing said acrylic composite fibers.

The present invention relates to porous acrylic synthetic fibers and acrylic composite fibers having a water absorption property and methods for producing these fibers.

Natural fibers, such as cotton, wools, silks and others have a water absorption property of 20-40% and absorb perspiration satisfactorily so that a pleasant feeling is obtained during wearing, but synthetic fibers are low in the antistatic property and the hygroscopicity and have no water absorption property and perspiration absorption property and therefore the synthetic fibers are inferior to natural fibers in the commercial value. Particularly, if underwears, stockings, blankets, sports wears, etc. have no water- and perspiration-absorption property, the perspiration condenses on the fiber surface and such fibers are sticky and cause a cold feeling and are poor in regulation of the body temperature and an unpleasant feeling when wearing can not be avoided.

For improving the water- and perspiration-absorption property of synthetic fibers, various improvements have been heretofore proposed. The major parts of the improvements consist in the formation of microvoids in the fibers or the formation of unevenness on the fiber surface. For example, Japanese Patent Laid Open Application No. 25,418/72, Japanese Patent Nos. 665,549 and 702,476 and Japanese Patent Application Publication No. 6,650/73 have disclosed processes for producing porous acrylic fibers by selecting such a mild drying condition that microvoids remain in the swelled gel tow during the production of acrylic fibers. Furthermore, Japanese Patent Laid Open Application No. 25,416/72, Japanese Patent Application Publication Nos. 8,285/73 and 8,286/73 have disclosed that a water soluble compound is incorporated in the swelled gel tow during the production of acrylic fibers and the swelled gel tow is dried and after-treated, after which the water soluble compound is dissolved off to reform the voids. The common concept in the above described processes consists in that microvoids inherently formed during the production of the acrylic fibers are maintained in the final product to obtain porous acrylic fibers. The microvoids formed in the swelled gel tow are very thermally unstable. Therefore, it is impossible to effect treatment at a high temperature in the steps for producing the fibers, particularly at the drying, shrinking and crimp setting steps and the heat resistance, form stability and crimp stability of the final product are poor and the commercial value of the product is considerably deteriorated. The radius of the voids in the obtained product is very small, such as 10-1,000 A. Since numerous microvoids are uniformly distributed in the fibers, the strength and elongation of the fibers are low, the luster is poor and the dyed color is not clear. Furthermore, since numerous microvoids are uniformly distributed, the heat resistance of the fibers is low and in a high temperature dyeing, steaming treatment, pressing treatment and the like, the voids are eliminated, the water absorption property is deteriorated, the color tone is varied, the form stability is deteriorated and the qualities are degraded.

When it is attempted to develop the water absorption property by these voids, the microvoids are apt to be formed as closed voids and they hardly form passages through which water is absorbed into the fibers and this proposal is not effective. In order to obtain a certain degree of water absorption property, a fairly large number of microvoids are necessary and this further deteriorates the fiber properties and commercial value. It has been previously attempted to improve the feel and the dyeability by mix-spinning of cellulose acetate-acrylic polymer or cellulose acetate-modacrylic copolymer. For example, Japanese Pat. Nos. 222,873 and 243,556 and Japanese Patent Application Publication No. 14,029/64 have disclosed that the spinning solution obtained by mixing cellulose acetate with acrylic polymer or modacrylic copolymer is spun to obtain fibers having improved dyeability and feel. The fibers obtained in these processes are dense and have no water absorption property due to voids in the fiber interior. In addition, Japanese Pat. No. 433,941 has disclosed that cellulose acetate is added during polymerization of the acrylic polymer as a means for mixing cellulose acetate, but when the polymer obtained by mixing cellulose acetate during polymerization of the acrylic polymer is used, the heat resistance of the spun fibers is deteriorated owing to the degradation of cellulose acetate and troubles occur during the steps for producing the fibers and the product having the satisfactory quality can not be obtained. Japanese Pat. No. 556,549 and Japanese Patent Laid Open Application Nos. 118,027/75 and 118,026/75 have described that cellulose acetate or a mixture of cellulose acetate and titanium oxide and the like is finely distributed in acrylic polymer or modacrylic polymer to obtain animal hair-like fibers but it can not provide porous fibers having a high water absorption property as is obtained in the present invention. German Patent Laid Open Application No. 2,901,778 has proposed acrylic fibers having a water absorption property, consisting of a porous core portion having a large number of microvoids and macrovoids and a skin portion having a high density, but these fibers have a large number of microvoids, so that the yarn property and dyeability are deteriorated. Further it is not easy to produce fibers having uniform microvoids and it is difficult to obtain fibers having stable quality. Fibers having excellent yarn property, heat resistance, dyeability and water absorption property as in the present invention can not be obtained by this procedure.

From the above described reasons, porous acrylic synthetic fibers having improved water absorption property, heat resistance, dyeability and luster can not be obtained by the prior presence.

Japanese Patent Application Publication No. 6,014/67 has disclosed acrylic composite fibers obtained by conjugate spinning acrylic polymers having different contents of ionic hydrophilic groups in which as a composite component having a smaller amount of said hydrophilic group, use is made of an acrylic polymer containing a cellulosic polymer which is obtained by solution polymerization of acrylic monomer in the presence of a cellulosic polymer soluble in a solvent for polymerization of the acrylic polymer. Japanese Pat. No. 520,657 has disclosed that in the conjugate spinning of acrylonitrile polymer containing an acidic group and acrylonitrile polymer containing a basic group, a cellulosic polymer is contained in a component having a lower shrinkage among these polymers. However, these processes aim to improve the crimpability and dyeability and to provide the resilient feeling of the cellulosic polymer but do not aim at porous acrylic composite fibers having a water absorption property and these fibers can not be obtained by these processes. The inventors have diligently studied to obviate the prior defects and accomplished the present invention.

An object of the present invention is to provide porous acrylic synthetic fibers and acrylic composite fibers having excellent water absorption property and good yarn properties.

Another object of the present invention is to provide methods for producing porous acrylic synthetic fibers and acrylic composite fibers having excellent water absorption property and good yarn properties commercially easily and cheaply.

The present invention consists in porous acrylic synthetic fibers having substantially no microvoids but having mainly macrovoids, which consist of 2˜30% by weight of cellulose acetate and 70˜98% by weight of an acrylic polymer and have a surface area A of voids of no greater than 15 m² /g and a porosity V of 0.05˜0.75 cm³ /g, V/A being 1/30 or more.

The process of the present invention comprises spinning an organic solvent solution containing 15˜35% by weight of a polymer consisting of 2˜30 parts by weight of cellulose acetate and 70˜98 parts by weight of an acrylic polymer into a coagulation bath at a temperature of no higher than 30° C. to obtain fibers wherein the formation of microvoids is restrained, effecting primary drawing of the spun fibers at a draw ratio of 2.5˜8 times, drying the fibers in a water swelled state having distributed macrovoids at a temperature of 100°˜180° C. to a water content of no greater than 1.0% by weight to substantially eliminate microvoids and effecting secondary drawing of the dried fibers under wet heat at a draw ratio of no greater than 3 times to promote the macrovoid structure.

Furthermore, the present invention relates to acrylic composite fibers and a method for producing said fibers, which is discussed later.

The acrylic synthetic fibers according to the present invention consist of 2˜30% by weight, preferably 3˜25% by weight, more preferably 6˜20% by weight, more particularly from more than 10% by weight to 18% by weight of cellulose acetate and 70˜98% by weight, preferably 75˜97% by weight, more preferably 80˜94% by weight, more particularly from 82% by weight to less than 90% by weight of an acrylic polymer. When the amount of cellulose acetate distributed in the fibers is less than 2% by weight, phase separation thereof from the acrylic polymer is insufficient and the satisfactory water absorption property can not be obtained, while when said amount exceeds 30% by weight, the phase separation becomes excessive and the strength and elongation, dyeability and luster of the fibers are deteriorated, so that these amounts should be avoided.

Cellulose acetate to be used in the present invention is not particularly limited but in general, is one having a combined acetic acid of 48˜63% and an average polymerization degree of 50˜300.

The acrylic polymers to be used in the present invention contain at least 80% by weight, preferably 85˜93% by weight of acrylonitrile and may contain less than 20% by weight of copolymerizable monomers, for example alkyl acrylates or methacrylates, such as methyl acrylate, methyl methacrylate, ethyl acrylate, amides, such as acrylamide, methacrylamide, N-mono-substituted or N,N-disubstituted amides thereof, vinyl acetate, sulfonic acid group-containing monomers, such as styrenesulfonic acid, allylsulfonic acid, methallylsulfonic acid and the salts thereof. In particular, when 0.3˜1.5% by weight, preferably 0.5˜1.2% by weight of allylsulfonic acid or methallylsulfonic acid or the salts thereof is copolymerized, the dyeability is not only improved, but also the formation of numerous microvoids is prevented, whereby the degradation of the heat resistance is prevented and porous fibers having macrovoids and excellent water absorption property can be obtained.

The acrylic polymer of the acrylic synthetic fibers according to the present invention may contain an acrylic copolymer containing 5˜30% by weight of a monomer having the general formula ##STR1## wherein X is R₂ or ##STR2## R₁ and R₃ are H or CH₃, R₂ is H, NH₄ or an alkali metal, and l and m are an integer of 0˜50 and 0<l+m≦50, and the acrylic copolymer is no greater than about 33% by weight based on the total polymer composing the acrylic synthetic fibers. By incorporating the above described acrylic copolymer in the acrylic synthetic fibers, the dispersability of cellulose acetate is improved. As the monomers to be copolymerized in the acrylic copolymers shown by the above described general formula, acrylic acid, methacrylic acid and ##STR3## are preferable in view of the polymerizability, discoloration and resistance to water solubility. As the length of the ethylene glycol chain or the propylene glycol chain contained in these monomers is larger, the hydrophilic property of the acrylic copolymer is increased and the content is permitted to be smaller, but when l+m exceeds 50, the polymerizability and solubility of the acrylic copolymer are degraded. As the monomers copolymerizable in the acrylic copolymer other than the monomers having the above described general formula, the above described monomers to be used in the polymerization of the acrylic polymers may be used. The acrylic copolymer contains at least 70% by weight of acrylonitrile.

The acrylic synthetic fibers according to the present invention have substantially no microvoids but have mainly macrovoids and the macrovoids contribute to the water absorption property. In the acrylic synthetic fibers according to the present invention, cellulose acetate is distributed in an elongated form having the longest dimension parallel to the fiber axis and generally has voids in the circumference and the inner portion of cellulose acetate and the ratio of the length to the diameter of the elongated cellulose acetate is generally 10 or more. The voids present in the distributed elongated cellulose acetate are macrovoids caused by the phase separation of cellulose acetate and acrylic polymer and are further elongated by the secondary drawing. The acrylic polymer component in the acrylic synthetic fibers of the present invention has substantially the same degree of denseness as usual acrylic synthetic fibers and has substantially no microvoids. The term "substantially no microvoids" used herein means that the ratio (by volume) of microvoids occupied in the porosity (V) of the fibers is not greater than 30%, preferably not greater than 25%, more preferably not greater than 20%, more particularly not greater than 15%. The term "microvoid" used herein means voids having a diameter of less than 2,000 A.

The water absorption property of the acrylic synthetic fibers according to the present invention can be obtained owing to these macrovoids and the ratio of the macrovoids occupied in the porosity is at least 70%, preferably at least 75%, more preferably at least 80%, more particularly at least 85%. Cellulose acetate is distributed not only in the inner portion of the cross section of the fiber but also in the fiber wall, so that macrovoids are observed at the fiber surface. The high water absorption property of the acrylic synthetic fibers of the present invention is presumably due to the fact that the voids opening at the fiber surface communicate with the macrovoids in the inner portion of the fibers.

Then, the acrylic synthetic fibers according to the present invention will be explained with reference to the accompanying drawings, wherein:

FIG. 1 is an optical photomicrograph (magnification: 200 times) of the cross-section of conventional acrylic fibers;

FIG. 2 is an optical photomicrograph (magnification: 200 times) of the cross section of porous acrylic fibers having a water absorption property, which contain cellulose acetate and in which a large number of microvoids are formed together with macrovoids;

FIG. 3 is an optical photomicrograph (magnification: 200 times) of the cross section of porous acrylic fibers of the present invention;

FIGS. 4, 5 and 6 are electron micrographs (magnification: 12,000 times) of the cross sections of the fibers shown in FIGS. 1˜3 respectively;

FIG. 7 is an electron micrograph (magnification: 12,000 times) of the cross section of conventional acrylic fiber having microvoids, and

FIG. 8 is an optical photomicrograph (magnification: 200 times) of the cross section of acrylic composite fibers of the present invention wherein an acrylic polymer (component A) containing cellulose acetate and an acrylic polymer (component B) are bonded in side-by-side relation.

In FIG. 2 and FIG. 3, fibers in which red dye stuff was impregnated so that the judgement of the presence of microvoids was made easy, were used as the samples.

As seen from FIG. 1, the usual acrylic fiber does not substantially have voids. In FIG. 2, since macrovoids are observed but the fibers have numerous microvoids, the dye stuff penetrates along the entire cross section of the fibers. In the fibers according to the present invention, as seen from FIG. 3, only macrovoids are observed and microvoids are not substantially observed.

The usual acrylic fiber in FIG. 4 is very dense and no microvoids are observed. FIG. 5 shows apparently that a large number of microvoids are present in the inner portion of the fiber. On the other hand, FIG. 6 shows that the fiber of the present invention has substantially the same density as the usual acrylic fiber at the portion other than macrovoids. The microvoid structure is apparently observed from FIG. 7 in the conventional acrylic fiber having the microvoid structure.

In the acrylic synthetic fibers of the present invention the surface area A of voids is no greater than 15 m² /g, preferably 0.02˜10 m² /g, a porosity V is 0.05˜0.75 cm³ /g, preferably 0.05˜0.60 cm³ /g and V/A is 1/30 or more, preferably 1/20 or more.

The surface area A(m² /g) of voids in the fibers was determined as follows. Nitrogen gas was adsorbed in the fibers at the temperature of liquid nitrogen, the total surface area of the fibers was determined by the BET equation and from this value was subtracted the surface area of the outer skin of the fibers. The amount of the fibers to be measured was adjusted so that the value of the total surface area to be measured is 1 m² or more.

The porosity V(cm³ /g) was determined as follows. A density ρ(g/cm³) of a film prepared so as to have the same composition as the fiber and a high density, was measured and an average cross sectional area of the fibers containing the voids was determined by photographic process and referred to as S(cm²) and an actual average cross sectional area So(cm²) of the fibers at the portion containing no voids was determined from the following equation (1) and the porosity V was determined from the following equation (2). ##EQU1##

The ratio of microvoids occupied in the porosity was calculated by measuring the microvoid content by means of a mercury porosimeter. Firstly, the fibers are opened and weighed and then filled in a cell of a mercury porosimeter and a pressure and an amount of mercury pressed in are recorded while pressing mercury at room temperature. Between a diameter D(μ) of the voids and a pressure P(psi) necessary for filling mercury in the voids, there is a relation shown by the following formula

    D=175/P

By measuring P and the amount of mercury pressed in the diameter D(μ) and the volume (cm³ /g) of the voids are determined. From these data, a void distribution curve is obtained and an amount of the voids in which D is 0.2μ or less is determined, which is referred to as the microvoid content (cm³ /g) in 1 g of the fibers.

When the porosity V is less than 0.05 cm³ /g, the water absorption property is not satisfied, while when the porosity V exceeds 0.75 cm³ /g, the strength and elongation of the fibers are degraded and the luster and dyeability are adversely affected, so that these values should be avoided.

When the surface area A of the voids exceeds 15 m² /g, the microvoids in the fibers increase and the strength and elongation are not only deteriorated but also the dyeability and heat resistance are deteriorated. When V/A is less than 1/30, the water absorption property is not satisfied or the heat resistance, dyeability and the like as well as the strength and elongation are deteriorated. Furthermore, it has been found from the experimental data of the inventors that when V/A is less than 1/30, the voids in the fibers become small and if the size is calculated into, for example a sphere, the diameter becomes less than 2,000 A and the excellent water absorption property can not be obtained and the strength and elongation are deteriorated.

The acrylic synthetic fibers according to the present invention are produced by spinning an organic solvent solution containing 15˜35% by weight, preferably 17˜30% by weight of a polymer consisting of 2˜30 parts by weight, preferably 3˜25 parts by weight, more preferably 6˜20 parts by weight, more particularly from more than 10 parts by weight to 18 parts by weight of cellulose acetate, and 70˜98 parts by weight, preferably 75˜97 parts by weight, more preferably 80˜94 parts by weight, more particularly 82˜90 parts by weight of an acrylic polymer or a blend of an acrylic polymer and an acrylic copolymer into a coagulation bath at a temperature of no higher than 30° C. When the amounts of cellulose acetate, an acrylic polymer or a blend of an acrylic polymer and an acrylic copolymer are beyond these ranges, acrylic synthetic fibers having an excellent water absorption property and yarn properties can not be obtained. When the concentration of the polymer is less than 15% by weight, the production cost becomes higher and the formation of microvoids increases to deteriorate the strength and elongation. While when the concentration exceeds 35% by weight, the viscosity increases, whereby the operability and spinnability are deteriorated and further the yarn properties are degraded, so that these amounts should be avoided.

As the organic solvent to be used in the present invention, mention may be made of common solvents for cellulose acetate, acrylic polymers and acrylic copolymers but in general, organic solvents, such as dimethylformamide, dimethylacetamide, dimethylsulfoxide, ethylene carbonate and the like are preferable in view of the recovery and purification of the solvents. As the coagulation bath, use may be made of an aqueous solution of an organic solvent, such as dimethylformamide, dimethylacetamide, dimethylsulfoxide, ethylene carbonate and the like, and organic solvents, such as propyl alcohol, kerosene and the like, but an aqueous solution of an organic solvent to be used for dissolving the polymer is particularly preferable.

The process for mixing cellulose acetate and an acrylic polymer or mixing an acrylic copolymer to said mixture is not particularly limited. For example, each of the polymers is dissolved in a common solvent and the obtained solutions are mixed or these polymers are concurrently added and dissolved in a common solvent.

Water may be added to the spinning solution within the range which does not cause gellation of the spinning solution. This addition of water is effective for controlling the viscosity of the spinning solution and preventing the formation of microvoids in the spun fibers. Interestingly, the inventors have found that the dispersed state of the elongated cellulose acetate in the spun fibers varies depending upon the water content in the spinning solution. Namely, when the water content in the spinning solution is increased, the dispersed state of the elongated cellulose acetate becomes longer, conversely as the water content decreases, the form becomes spherical. A similar result is obtained depending upon the variation of the viscosity of the spinning solution.

The spinning can be carried out under the same conditions as are employed for preparing conventional acrylic synthetic fibers except that the temperature of the coagulation bath cannot be higher than 30° C. Several stages of spinning baths are used and the primary drawing and water washing are carried out. The primary draw ratio is 2.5˜8 times, preferably 3˜6 times. When the primary draw ratio is less than 2.5 times, the drawing and orientation of the fibers are insufficient and therefore the strength is low and cracks are formed in the fibers and such a drawing should be avoided. While, when the draw ratio exceeds 8 times, the densification excessively proceeds and a satisfactory water absorption property can not be obtained and the operability is deteriorated, so that such draw ratios should be avoided.

The spinning draft ratio may be the usual condition, but for restraining the formation of microvoids a lower draft ratio is preferable. The temperature of the coagulation bath for restraining the formation of microvoids must be not higher than 30° C., preferably not higher than 25° C., more preferably not higher than 20° C. When the temperature of the coagulation bath is higher than 30° C., a large number of microvoids are formed and the yarn properties and quantity of the obtained fibers are considerably deteriorated.

In the primary drawn fibers, the dispersion of the elongated cellulose acetate, and the voids formed by the phase separation of cellulose acetate and the acrylic polymer become more distinct. But the fibers contain a large number of microvoids inherently contained in the usual swelled gel tow. These microvoids are not desirable because of the deterioration of the heat resistance, dyeability and luster of the fibers. Hence, the fibers wherein the microvoids and macrovoids coexist, are dried to eliminate the microvoids but, in this case, the drying is carried out at a temperature of 100°˜180° C., preferably 105°˜150° C. until the water content becomes no greater than 1.0% by weight, whereby only the microvoids are eliminated and the macrovoids formed due to the phase separation are maintained. When the drying temperature is lower than 100° C., the microvoids formed in the acrylic polymer can not be completely collapsed by drying and the strength and elongation, luster, dyeability and heat resistance of the fibers are deteriorated. While when the drying temperature exceeds 180° C., the fibers are hardened and discolored, so that such a temperature should be avoided. For drying, it is desirable for eliminating the microvoids to use a hot roller type dryer in which the fibers are brought into contact with a metal surface heated at a high temperature. In addition, if the drying is effected by blowing hot air at a temperature of 120°˜170° C. as a supplemental means, the drying can be effected more uniformly, so that such a means is desirable. The water content of the dried fibers must be no greater than 1.0%. When the water content exceeds 1.0%, the uneven drying of the fibers occurs and a large number of microvoids partially remain resulting in unevenness of dyeing, luster and strength of the fibers and the uniformity of quality is deteriorated. In this drying step, a torque motor may be used to effect shrinkage of 5˜15% together with the drying.

The dried fibers should be subjected to a secondary drawing under wet heat to a draw ratio of no greater than 3 times, preferably 1.05˜2 times in order to make the phase separation of the acrylic polymer and cellulose acetate in the fibers more distinct and to promote the macrovoid structure and improve the water absorption property and provide moderate physical properties of the fiber. The secondary drawing includes stretching shrinkage of substantial draw ratio of no greater than 1.0. But in order to elongate the macrovoid structure, the draw ratio is preferred to be at least 1.05, particularly at least 1.1. When the draw ratio exceeds 3 times, yarn breakage occurs and if the temperature is raised in order to prevent yarn breakage, stickiness of the fibers occurs and the water absorption property is considerably deteriorated. After the secondary drawing, the fibers are subjected to after-treating steps for imparting good spinnability and performance to the fibers, such as wet heat shrinking step, oiling step, crimping step and crimp-setting step to obtain the final product.

Now, an explanation will be made with respect to acrylic composite fibers according to the present invention. The composite fibers according to the present invention are ones having a water absorption property obtained by bonding a component A consisting of 2˜50% by weight of cellulose acetate and 50˜98% by weight of an acrylic polymer and a component B consisting of an acrylic polymer in a weight ratio of 2/8˜8/2 along the fiber axial direction, the component A having substantially no microvoids but having mainly macrovoids, and having a porosity of the entire fibers of 0.05˜0.75 cm³ /g and a surface area of voids of no greater than 15 m² /g, or ones having a water absorption property and latent crimpability obtained by eccentrically bonding two components A and B consisting of 2˜50% by weight of cellulose acetate and 50˜98% by weight of an acrylic polymer, a plasticizing component in the acrylic polymer in both the components A and B having a difference of at least 2% by weight, in a weight ratio of 7/3˜3/7, a total amount of cellulose acetate in the fibers being 2˜30% by weight, having substantially no microvoids but having macrovoids, and having a porosity of 0.05˜0.75 cm³ /g and a surface area of voids of no greater than 15 m² /g.

The process for producing the composite fibers according to the present invention comprises conjugate spinning two organic solvent solutions A and B in which at least one solution contains a polymer consisting of 2˜50% by weight of cellulose acetate and 50˜98% by weight of an acrylic polymer, into a coagulation bath at a temperature of no higher than 30° C. through common spinning orifices to form composite fibers in which the formation of microvoids is restrained, effecting primary drawing the spun fibers in a draw ratio of 2.5˜8 times, drying the water swelled fibers containing distributed macrovoids at a temperature of 100°˜180° C. to a water content of no greater than 1.0% by weight to substantially eliminate microvoids and then effecting secondary drawing of the dried fibers in a draw ratio of no greater than 3 times under wet heat to promote the macrovoid structure.

In the case of acrylic composite fibers in which only the component A contains cellulose acetate, when an amount of a plasticizing component in acrylic polymers composing the components A and B, such as methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, acrylamide, vinyl acetate, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate and the like is different in an amount of at least 2% by weight and the component A and the component B are conjugate spun eccentrically, composite fibers having latent crimpability can be obtained. On the other hand, when there is substantially no difference in the content of the above described plasticizing component in the acrylic polymers to composing the component A and the component B or both the components are concentrically conjugate spun, composite fibers having substantially no latent crimpability can be obtained.

The component A and the component B are bonded in a conjugate ratio of 2/8˜8/2, preferably 3/7˜7/3, more preferably 4/6˜6/4. If the component A is smaller than 2/8 in the conjugate ratio, a satisfactory water absorption property can not be given to the composite fibers, while if the component A exceeds 8/2, the luster and color brightness after dyeing are deteriorated. As the plasticizing components in both the components A and B to be used in the acrylic composite fibers containing cellulose acetate, mention may be made of the above described compounds. The difference of the content of the plasticizing in both the components is at least 2% by weight, preferably 2.5˜5% by weight. The components A and B are bonded eccentrically, preferably in side-by-side relation.

When the difference of the content of the above described plasticizing component is less than 2% by weight, it is impossible to obtain composite fibers having substantial the latent crimpability. The component A and the component B are bonded in a conjugate ratio of 3/7˜7/3, preferably 4/6˜6/4. When the ratio exceeds this range, composite fibers having excellent crimpability can not be obtained. The conjugate ratio of the acrylic composite fibers according to the present invention can be conveniently varied by varying the extruded amount of the solutions of the components A and B in an organic solvent or the polymer concentration.

When the component A or both the components A and B contain cellulose acetate, the amount of cellulose acetate is 2˜50% by weight, preferably 3˜40% by weight, more preferably 5˜30% by weight. When the amount of cellulose acetate distributed in the component A or both the components A and B is less than 2% by weight, the phase separation of the acrylic polymer is insufficient and the water absorption property can not be satisfied, while when said amount exceeds 50% by weight, the strength and elongation in the component A or both the components A and B become considerably lower and both the components are disengaged, so that these amounts should be avoided.

When cellulose acetate in contained in both the components A and B, the total amount of cellulose acetate contained in both the components A and B is 2˜30% by weight, preferably 2˜25% by weight, more preferably 3˜20% by weight. When the total amount is less than 2% by weight, the water absorption property is not satisfied and when said amount exceeds 30% by weight, the yarn properties, such as strength and elongation of the composite fibers are deteriorated and these amounts should be avoided.

Concerning the acrylic polymers, acrylic copolymers and cellulose acetate to be used for the acrylic composite fibers according to the present invention, the above described explanation concerning the acrylic synthetic fibers can be applied.

Cellulose acetate in at least one component of the composite fibers of the present invention is distributed in an elongated form parallel to the fiber axis, and generally has voids around the elongated cellulose acetate and in the inner portion and the ratio of the length of the distributed elongated cellulose acetate to the diameter thereof is usually 10 or more.

The component containing cellulose acetate in the composite fibers of the present invention does not substantially have microvoids but has mainly macrovoids and these macrovoids contribute to the water absorption property.

FIG. 8 is an optical photomicrograph (magnification: 200 times) of the cross section of the acrylic composite fibers of the present invention in which the component A (acrylic polymer containing cellulose acetate) and the component B (acrylic polymer) are bonded in side-by-side relation and it can be seen from FIG. 8 that macrovoids are observed in the component A and the component B is dense.

The acrylic composite fibers of the present invention have a porosity of 0.05˜0.75 cm³ /g, preferably 0.05˜0.60 cm³ /g and a surface area of voids of no greater than 15 m² /g, preferably 0.02˜10 m² /g as the entire fibers.

When the porosity is less than 0.05 cm³ /g, the water absorption property is not satisfactory, while when the porosity exceeds 0.75 cm³ /g, the strength and elongation of the fibers not only are deteriorated, but also the luster and dyeability are adversely affected.

When the surface area of the voids exceeds 15 m² /g, microvoids increase in the fibers and the strength and elongation decrease and the dyeability and heat resistance are deteriorated.

The organic solvent, coagulation bath condition, and spinning and drawing conditions in the production of the acrylic composite fibers are similar to those in the above described production of acrylic synthetic fibers.

After the secondary drawing, the composite fibers having the latent crimpability may be subjected to after-treatments, such as shrinkage-drawing-shrinking in order to enhance the crimpability. After the secondary drawing, the fibers are subjected to after-treatments for giving high spinnability and properties, such as shrinking under wet heat, oiling, crimping, crimp setting and the like, to obtain the final product.

The composite fibers of the present invention can easily develop crimps through hot water treatment and steam treatment.

The porous acrylic synthetic fibers and the acrylic composite fibers according to the present invention can be produced by using not only an organic solvent but also an inorganic solvent, such as aqueous solution of zinc chloride and the like.

The porous acrylic synthetic fibers obtained by the present invention have a high water absorption property and water absorbing rate and are excellent in strength and elongation under wet swelling when absorbing water, and have good luster and brightness when dyed. The acrylic composite fibers of the present invention have a high water absorption property, water absorbing rate, excellent strength and elongation when absorbing water, good dyeability and unique bulkiness and rich feeling of the inherent composite fibers.

In the natural fibers, the bulkiness and resilient feeling are lost upon wet swelling but in the acrylic synthetic fibers and acrylic composite fibers according to the present invention, the water absorption is a physical mechanism in which water is absorbed in voids in the fibers, so that these fibers are not deteriorated in the bulkiness and resilient feeling and the water absorption property, water- and moisture-permeability are excellent. In addition, acrylic synthetic fibers and composite fibers according to the present invention have a porosity of 0.05˜0.75 cm³ /g and are light in weight and very high in the heat retaining property.

The acrylic synthetic fibers and composite fibers of the present invention, which have such many excellent properties, are optimum for general clothings, sports wears, bedding, curtains, interior and the like. Furthermore, these fibers are satisfactorily used in the field where cotton has been used, as cotton substitutes.

The following examples are given for the purpose of illustration of this invention and are not intended as limitations thereof. In the examples, parts and % mean parts by weight and % by weight unless otherwise indicated. The water absorption of fibers was measured according to DIN-53814, and the crimp property thereof was measured according to JIS L-1074.

EXAMPLE 1

A dimethyl formamide (hereinafter abbreviated as DMF) solution containing 21% of a polymer mixture consisting of an acrylic polymer and cellulose acetate in a mixing ratio shown in the following Table 1 was extruded from a spinneret into a coagulation bath consisting of 65% of DMF and 35% of water and kept at 20° C. The acrylic polymer had a composition of acrylonitrile (hereinafter abbreviated as AN):methyl acrylate (hereinafter abbreviated as MA):sodium methallylsulfonate (hereinafter abbreviated as SMAS)=90.5:9.0:0.5(%). The extruded filaments were subjected to a primary drawing to draw the filaments to 5 times their original length, and then dried by means of a hot roller type drier kept at 120° C. until the water content of the filaments was decreased to 0.5%. The dried filaments were subjected to a secondary drawing at 100° C. under wet heat to draw the filaments to 1.1 times their original length. The drawn filaments were mechanically crimped and the crimps were set to obtain 3-denier fibers. Properties of the resulting fibers are shown in Table 1. It was found that the ratios of microvoids in the fibers of Experiment Nos. 4 and 5 were 11.3% and 14.6%, respectively.

                                      TABLE 1                                      __________________________________________________________________________                                 Fiber property                                     Polymer mixture                                                                               Void         Water                                              Experi-                                                                             Acrylic                                                                             Cellulose                                                                           Porosity,                                                                           Surface absorp-                                            ment polymer                                                                             acetate                                                                             V    area, A tion                                                                               Strength                                       number                                                                              (parts)                                                                             (parts)                                                                             (cm.sup.3 /g)                                                                       (m.sup.2 /g)                                                                        V/A                                                                               (%) (g/d)                                                                               Dyeability                                                                           Remarks                             __________________________________________________________________________     1    100  0    0.000                                                                               0.00 -- 4   3.8  good  Comparative                                                                    sample                              2    99   1    0.021                                                                               0.57                                                                                 ##STR4##                                                                         4   3.8  good  Comparative sample                  3    98   2    0.116                                                                               1.62                                                                                 ##STR5##                                                                         15  3.8  good  Present invention                   4    95   5    0.221                                                                               1.70                                                                                 ##STR6##                                                                         25  3.6  good  Present invention                   5    90   10   0.357                                                                               2.04                                                                                 ##STR7##                                                                         38  3.2  good  Present invention                   6    80   20   0.46 2.35                                                                                 ##STR8##                                                                         48  2.6  somewhat poor                                                                        Present invention                   7    70   30   0.588                                                                               2.76                                                                                 ##STR9##                                                                         60  1.7  somewhat poor                                                                        Present invention                   8    65   35   0.798                                                                               3.09                                                                                 ##STR10##                                                                        80  1.1  poor  Comparative sample                  9    60   40   1.08 3.09                                                                                 ##STR11##                                                                        100 0.8  poor  Comparative sample                  __________________________________________________________________________

EXAMPLE 2

The same acrylic polymer as used in Example 1 was used, and 3-denier fibers shown in the following Table 2 were produced by changing the composition of the polymer mixture, the extruding condition, the drawing condition, the drying condition and other production conditions. Properties of the resulting fibers are shown in Table 2.

                                      TABLE 2(a)                                   __________________________________________________________________________     Void              Fiber property                                               Experi-                                                                             Porosity,                                                                           Surface Water                                                        ment V    area, A absorption                                                   number                                                                              (cm.sup.3 /g)                                                                       (m.sup.2 /g)                                                                        V/A                                                                               (%)   Others     Remarks                                     __________________________________________________________________________     10   0.03 0.71                                                                                 ##STR12##                                                                        5     poor in heat resistance and in dyeability                                                 Comparative sample                          11   0.05 1.82                                                                                 ##STR13##                                                                        9     poor in heat resistance and in dyeability                                                 Comparative sample                          12   0.10 0.44                                                                                 ##STR14##                                                                        14               Present invention                           13   0.35 2.11                                                                                 ##STR15##                                                                        37               Present invention                           14   0.75 17.3                                                                                 ##STR16##                                                                        70    low strength and poor dyeability                                                          Comparative sample                          15   0.90 25.1                                                                                 ##STR17##                                                                        87    low strength and poor dyeability                                                          Comparative sample                          16   1.05 9.83                                                                                 ##STR18##                                                                        104   low strength and poor dyeability                                                          Comparative sample                          17   0.43 0.94                                                                                 ##STR19##                                                                        45               Present invention                           __________________________________________________________________________

                                      TABLE 2(b)                                   __________________________________________________________________________     Void              Fiber property                                               Experi-                                                                             Porosity,                                                                           Surface Water                                                        ment V    area, A absorption                                                   number                                                                              (cm.sup.3 /g)                                                                       (m.sup.2 /g)                                                                        V/A                                                                               (%)   Others     Remarks                                     __________________________________________________________________________     18   0.59 0.78                                                                                 ##STR20##                                                                        60               Present invention                           19   0.30 13.8                                                                                 ##STR21##                                                                        33    poor in heat resistance and in dyeability                                                 Comparative sample                          20   0.61 16.8                                                                                 ##STR22##                                                                        63    low strength and poor dyeability                                                          Comparative sample                          21   0.51 19.1                                                                                 ##STR23##                                                                        50    low strength and poor dyeability                                                          Comparative sample                          22   0.80 26.9                                                                                 ##STR24##                                                                        76    poor in heat resistance and in dyeability                                                 Comparative sample                          23   0.72 0.95                                                                                 ##STR25##                                                                        73               Present invention                           24   0.63 3.21                                                                                 ##STR26##                                                                        64               Present invention                           __________________________________________________________________________

EXAMPLE 30

A polymer mixture consisting of 80 parts of an acrylic polymer, which had a composition of AN:MA:sodium allylsulfonate (hereinafter abbreviated as SAS)=90.2:9.0:0.8(%), and 20 parts of cellulose acetate was dissolved in a solvent shown in the following Table 3 to prepare spinning solutions having a property shown in Table 3. The extrusion of the spinning solution and the after-treatment of the extruded filaments were carried out under the same conditions as described in Example 1 to obtain 3-denier fibers. However, as the coagulation bath, an aqueous solution containing the same solvent as that used in the spinning solution was used.

Properties of the fibers are shown in Table 3. In Table 3, the viscosity of the spinning solution was measured at 50° C. by means of a Brookfield viscometer. The stability of the spinning solution was estimated by the stability against gellation at 50° C. and by the stability of dispersion of the acrylic polymer and cellulose acetate in the spinning solution.

                                      TABLE 3(a)                                   __________________________________________________________________________     Spinning solution                                                                         Concent-                    Fiber property                                     ration of      Void         Water                                   Experi-    polymer        Porosity,                                                                           Surface absorp-                                 ment       mixture                                                                             Viscosity V    area, A tion                                                                               Strength                            number                                                                              Solvent                                                                              (%)  (poise)                                                                             Stability                                                                           (cm.sup.3 /g)                                                                       (m.sup.2 /g)                                                                        V/A                                                                               (%) (g/d)                                                                               Operability                                                                           Remarks                 __________________________________________________________________________     25   Dimethyl acetamide                                                                   10   8.5  good 0.57 17.9                                                                                 ##STR27##                                                                        58  1.8  somewhat poor                                                                         Comparative                                                                    sample                  26   Dimethyl acetamide                                                                   15   15   good 0.51 3.14                                                                                 ##STR28##                                                                        53  1.9  good   Present invention       27   Dimethyl acetamide                                                                   20   76   good 0.48 2.62                                                                                 ##STR29##                                                                        50  2.5  good   Present invention       28   Dimethyl acetamide                                                                   25   210  good 0.46 2.48                                                                                 ##STR30##                                                                        48  2.7  good   Present invention       29   Dimethyl acetamide                                                                   30   640  good 0.47 2.24                                                                                 ##STR31##                                                                        49  2.6  good   Present invention       30   Dimethyl acetamide                                                                   35   >1,000                                                                              somewhat poor                                                                       0.43 1.96                                                                                 ##STR32##                                                                        45  2.4  somewhat poor                                                                         Present invention       31   Dimethyl acetamide                                                                   40   gelled                                                                              poor 0.42 1.86                                                                                 ##STR33##                                                                        44  2.1  poor   Comparative             __________________________________________________________________________                                                            sample             

                                      TABLE 3(b)                                   __________________________________________________________________________     Spinning solution                                                                         Concent-                      Fiber property                                   ration of        Void         Water                                 Experi-    polymer          Porosity,                                                                           Surface absorp-                               ment       mixture                                                                             Viscosity   V    area, A tion                                                                               Strength                          number                                                                              Solvent                                                                              (%)  (poise)                                                                              Stability                                                                            (cm.sup.3 /g)                                                                       (m.sup.2 /g)                                                                        V/A                                                                               (%) (g/d)                                                                               Operability                                                                          Remarks                __________________________________________________________________________     32   Dimethyl formamide                                                                   10   5.6   good  0.56 18.4                                                                                 ##STR34##                                                                        56  2.1  somewhat poor                                                                        Comparative                                                                    sample                 33   Dimethyl formamide                                                                   15   15    good  0.49 2.70                                                                                 ##STR35##                                                                        52  2.6  good  Present invention                                                              3                      34   Dimethyl formamide                                                                   20   50    good  0.46 2.35                                                                                 ##STR36##                                                                        48  2.6  good  Present invention                                                              1                      35   Dimethyl formamide                                                                   25   140   good  0.47 2.31                                                                                 ##STR37##                                                                        49  2.7  good  Present invention                                                              3                      36   Dimethyl formamide                                                                   30   420   good  0.46 2.26                                                                                 ##STR38##                                                                        48  2.9  good  Present invention                                                              .                      37   Dimethyl formamide                                                                   35   1,200 somewhat poor                                                                        0.41 2.95                                                                                 ##STR39##                                                                        43  2.7  somewhat poor                                                                        Present invention      38   Dimethyl formamide                                                                   40   gelled                                                                               poor  0.43 2.75                                                                                 ##STR40##                                                                        45  2.6  poor  Comparative            __________________________________________________________________________                                                             sample            

                                      TABLE 3(c)                                   __________________________________________________________________________     Spinning solution                                                                        Concent-                       Fiber property                                   ration of       Void          Water                                 Experi-   polymer          Porosity,                                                                           Surface  absorp-                               ment      mixture                                                                              Viscosity  V    area, A  tion                                                                               Strength                          number                                                                              Solvent                                                                             (%)   (poise)                                                                             Stability                                                                            (cm.sup.3 /g)                                                                       (m.sup.2 /g)                                                                        V/A (%) (g/d)                                                                               Operability                                                                          Remarks                __________________________________________________________________________     39   Dimethyl sulfoxide                                                                  10    15   good  0.50 16.1                                                                                 ##STR41##                                                                         49  2.3  somewhat poor                                                                        Comparative                                                                    sample                 40   Dimethyl sulfoxide                                                                  15    44   good  0.46 3.15                                                                                 ##STR42##                                                                         47  2.4  good  Present invention      41   Dimethyl sulfoxide                                                                  20    130  good  0.44 2.15                                                                                 ##STR43##                                                                         46  2.7  good  Present invention      42   Dimethyl sulfoxide                                                                  25    390  good  0.45 2.35                                                                                 ##STR44##                                                                         48  2.6  good  Present invention      43   Dimethyl sulfoxide                                                                  30    1,100                                                                               good  0.43 2.21                                                                                 ##STR45##                                                                         45  2.4  good  Present invention      44   Dimethyl sulfoxide                                                                  35    gelled                                                                              somewhat poor                                                                        0.39 2.16                                                                                 ##STR46##                                                                         41  2.3  somewhat poor                                                                        Present invention      45   Dimethyl sulfoxide                                                                  40    gelled                                                                              poor  0.36 2.03                                                                                 ##STR47##                                                                         38  2.0  poor  Comparative            __________________________________________________________________________                                                             sample            

EXAMPLE 4

A polymer mixture consisting of 90 parts of an acrylic polymer, which had a composition of AN:MA:SMAS=90.5:9.0:0.5(%), and 10 parts of cellulose acetate was dissolved in DMF to prepare a spinning solution containing 25% of the polymer mixture. The spinning solution was extruded from a spinneret into a coagulation bath consisting of 65% of DMF and 35% of water and kept at 25° C., and the extruded filaments were subjected to a primary drawing in various draw ratios shown in the following Table 4. The primarily drawn filaments were dried and after-treated under the same conditions as described in Example 1 to obtain 3-denier fibers. Properties of the resulting fibers are shown in Table 4.

                                      TABLE 4                                      __________________________________________________________________________                Void           Fiber property                                       Experi-                                                                             Draw ratio                                                                           Porosity                                                                             Surface  Water                                                ment in primary                                                                           V     area, A  absorption                                           number                                                                              drawing                                                                              (cm.sup.3 /g)                                                                        (m.sup.2 /g)                                                                        V/A (%)   Others       Remarks                           __________________________________________________________________________     46   1.5   0.381 3.05                                                                                 ##STR48##                                                                         40.3  dried filaments are brittle, and                                               operability thereof is poor                                                                 Comparative sample                47   2     0.362 2.01                                                                                 ##STR49##                                                                         38.5  dried filaments are brittle, and                                               operability thereof is poor                                                                 Comparative sample                48   3     0.368 1.99                                                                                 ##STR50##                                                                         39.0               Present invention                 49   4     0.352 2.01                                                                                 ##STR51##                                                                         37.5               Present invention                 50   5     0.337 1.71                                                                                 ##STR52##                                                                         36.1               Present invention                 51   6     0.326 1.58                                                                                 ##STR53##                                                                         35.0               Present invention                 52   7     0.294 1.75                                                                                 ##STR54##                                                                         32.0               Present invention                 53   8     0.126 0.84                                                                                 ##STR55##                                                                         16.0               Present invention                 54   9     0.04  0.28                                                                                 ##STR56##                                                                          8.0  yarn breakage occurs often                                                                  Comparative sample                __________________________________________________________________________

EXAMPLE 5

A polymer mixture consisting of 90 parts of an acrylic polymer, which had a composition of AN:MA:SMAS=92.5:7.0:0.5(%), and 10 parts of cellulose acetate was dissolved in DMF to prepare a spinning solution containing 25% of the polymer mixture, and the spinning solution was extruded from a spinneret into a coagulation bath consisting of 60% of DMF and 40% of water and kept at 30° C. The extruded filaments were subjected to a primary drawing to draw the filaments to 4.0 times their original length, and then dried until the water content of the filaments was decreased to not more than 0.5% by means of a hot roller type drier kept at a drying temperature shown in the following Table 5. The dried filaments were then subjected to a secondary drawing at 110° C. under wet heat to draw the filaments to 2 times their original length, and then mechanically crimped, and the crimps were set to obtain 3-denier fibers. Properties of the fibers are shown in Table 5.

                                      TABLE 5                                      __________________________________________________________________________     Drying    Void           Fiber property                                         Experi-                                                                            tempera-                                                                            Porosity,                                                                            Surface  Water                                                 ment ture V     area, A  absorption                                            number                                                                              (°C.)                                                                        (cm.sup.3 /g)                                                                        (m.sup.2 /g)                                                                        V/A (%)   Others       Remarks                            __________________________________________________________________________     55   60   0.60  26.4                                                                                 ##STR57##                                                                         56.1  poor in yarn property and in                                                                Comparative sample                 56   80   0.57  19.6                                                                                 ##STR58##                                                                         50.3  poor in yarn property and in                                                                Comparative sample                 57   100  0.50  7.5                                                                                  ##STR59##                                                                         51.6               Present invention                  58   120  0.41  2.34                                                                                 ##STR60##                                                                         43.0               Present invention                  59   140  0.35  1.89                                                                                 ##STR61##                                                                         37.3               Present invention                  60   150  0.30  1.61                                                                                 ##STR62##                                                                         32.6               Present invention                  61   160  0.25  1.30                                                                                 ##STR63##                                                                         27.8               Present invention                  62   180  0.23  1.18                                                                                 ##STR64##                                                                         25.9               Present invention                  63   190  0.21  1.05                                                                                 ##STR65##                                                                         24.0  fiber colors, and becomes                                                                   Comparative sample                 64   200  0.21  0.97                                                                                 ##STR66##                                                                         24.0  fiber colors, and becomes                                                                   Comparative sample                 __________________________________________________________________________

EXAMPLE 6

A polymer mixture consisting of 85 parts of an acrylic polymer, which had a composition of AN:MA:SAS=89:10.4:0.6(%), and 15 parts of cellulose acetate was dissolved in DMF to prepare a spinning solution containing 27% of the polymer mixture, and the spinning solution was extruded from a spinneret into a coagulation bath consisting of 70% of DMF and 30% of water and kept at 30° C. The extruded filaments were subjected to a primary drawing to draw the filaments to 5 times their original length, and the primarily drawn filaments were dried by means of a hot roller type drier kept at 125° C. to decrease the water content of the filaments to the water content shown in the following Table 6, and the dried filaments were subjected to the same aftertreatments as those described in Example 1 to obtain 2-denier fibers.

Properties of the fibers are shown in Table 6. Further, the fibers of Experiment Nos. 67 and 69 had ratios of microvoids of 15.3% and 14.2%, respectively.

                                      TABLE 6                                      __________________________________________________________________________               Void           Fiber property                                        Experi-                                                                             Water                                                                               Porosity,                                                                            Surface  Water                                                 ment content                                                                             V     area, A  absorption                                            number                                                                              (%)  (cm.sup.3 /g)                                                                        (m.sup.2 /g)                                                                        V/A (%)   Others     Remarks                              __________________________________________________________________________     65   0    0.433 2.68                                                                                 ##STR67##                                                                         45.2             Present invention                    66   0.1  0.457 3.23                                                                                 ##STR68##                                                                         47.5             Present invention                    67   0.2  0.505 3.65                                                                                 ##STR69##                                                                         52.1             Present  invention                   68   0.3  0.546 4.10                                                                                 ##STR70##                                                                         56.0             Present invention                    69   0.5  0.582 4.42                                                                                 ##STR71##                                                                         59.4             Present invention                    70   1.0  0.648 5.18                                                                                 ##STR72##                                                                         65.7             Present invention                    71   2.0  0.694 27.76                                                                                ##STR73##                                                                         70.1  low strength and poor dyeability, and                                          uneven property                                                                           Comparative sample                   72   5.0  0.717 29.5                                                                                 ##STR74##                                                                         72.3  low strength and poor dyeability, and                                          uneven property                                                                           Comparative sample                   __________________________________________________________________________

EXAMPLE 7

The same spinning solution as that used in Example 6 was extruded from a spinneret into a coagulation bath consisting of 65% of DMF and 35% of water and kept at 25° C., and the extruded filaments were subjected to a primary drawing to draw the filaments to 4 times their original length. Then, the primarily drawn filaments were dried by means of a hot roller type drier kept at 125° C. until the water content of the filaments was decreased to not more than 0.7%. The dried filaments were subjected to a secondary drawing under the same secondary drawing condition as described in Example 5 and then mechanically crimped, and the crimps were set to obtain 3-denier fibers. Properties of the fibers are shown in the following Table 7.

                                      TABLE 7(a)                                   __________________________________________________________________________     Secondary        Void          Fiber property                                  Experi-                                                                             drawing condition                                                                         Porosity,                                                                            Surface  Water                                           ment Temperature                                                                           Draw                                                                               V     area, A  absorption                                      number                                                                              (°C.)                                                                          ratio                                                                              (cm.sup.3 /g)                                                                        (m.sup.2 /g)                                                                        V/A (%)   Others  Remarks                           __________________________________________________________________________     73   100    0.9 0.333 2.18                                                                                 ##STR75##                                                                         35.7          Present invention                 74   "      1.0 0.334 2.20                                                                                 ##STR76##                                                                         36.8          Present invention                 75   "      1.5 0.338 2.24                                                                                 ##STR77##                                                                         36.2          Present invention                 76   "      2   0.297 2.32                                                                                 ##STR78##                                                                         32.3          Present invention                 77   "      3   0.222 2.50                                                                                 ##STR79##                                                                         25.1  yarn breakage occurs                                                                   Present invention                 78   110    0.9 0.326 2.08                                                                                 ##STR80##                                                                         35.0          Present invention                 79   "      1.0 0.359 2.12                                                                                 ##STR81##                                                                         37.0          Present invention                 80   "      2   0.332 2.16                                                                                 ##STR82##                                                                         35.6          Present invention                 __________________________________________________________________________

                                      TABLE 7(b)                                   __________________________________________________________________________     Secondary        Void          Fiber property                                  Experi-                                                                             drawing condition                                                                         Porosity,                                                                            Surface  Water                                           ment Temperature                                                                           Draw                                                                               V     area, A  absorption                                      number                                                                              (°C.)                                                                          ratio                                                                              (cm.sup.3 /g)                                                                        (m.sup.2 /g)                                                                        V/A (%)   Others  Remarks                           __________________________________________________________________________     81   110    3   0.294 2.24                                                                                 ##STR83##                                                                         32.0  yarn breakage occurs                                                                   Present invention                 82   "      4   0.158 2.44                                                                                 ##STR84##                                                                         19.0  frequent yarn breakage                                                                 Comparative sample                83   120    0.8 0.286 1.80                                                                                 ##STR85##                                                                         31.2          Present invention                 84   "      1   0.323 1.82                                                                                 ##STR86##                                                                         34.8          Present invention                 85   "      2   0.329 1.84                                                                                 ##STR87##                                                                         35.1          Present invention                 86   "      3   0.297 2.02                                                                                 ##STR88##                                                                         32.3          Present invention                 87   "      4   0.169 2.46                                                                                 ##STR89##                                                                         20.1  yarn breakage occurs                                                                   Comparative sample                88   "      5   --    --   --  --    spinning is                                                                            Comparative                                                            impossible                                                                             sample                            __________________________________________________________________________

                                      TABLE 7(c)                                   __________________________________________________________________________     Secondary       Void           Fiber property                                  Experi-                                                                             drawing condition                                                                         Porosity,                                                                            Surface  Water                                           ment Temperature                                                                           Draw                                                                               V     area, A  absorption                                      number                                                                              (°C.)                                                                          ratio                                                                              (cm.sup.3 /g)                                                                        (m.sup.2 /g)                                                                        V/A (%)   Others  Remarks                           __________________________________________________________________________     89   130    0.8 0.295 1.52                                                                                 ##STR90##                                                                         32.0          Present invention                 90   "      1   0.339 1.50                                                                                 ##STR91##                                                                         36.0          Present invention                 91   "      2   0.327 1.60                                                                                 ##STR92##                                                                         35.1          Present invention                 92   "      3   0.280 1.80                                                                                 ##STR93##                                                                         30.7          Present invention                 93   "      4   0.173 2.04                                                                                 ##STR94##                                                                         20.4  yarn breakage occurs                                                                   Comparative sample                94   "      5   --    --   --  --     spinning is                                                                           Comparative                                                            impossible                                                                             sample                            __________________________________________________________________________

EXAMPLE 8

A polymer mixture consisting of 80 parts of an acrylic polymer, which had a composition of AN:MA:SMAS=90.5:9.0:0.5(%), and 20 parts of cellulose acetate was dissolved in DMF to prepare a DMF solution containing 20% of the polymer mixture. Then, 100 parts of the DMF solution was mixed with 2 parts of water to prepare a spinning solution, and the spinning solution was extruded from a spinneret into a coagulation bath consisting of 50% of DMF and 50% of water and kept at 25° C. The extruded filaments were washed with water and then subjected to a primary drawing in hot water to draw the filaments to 4 times their original length. The primarily drawn filaments was dried until the water content of the filaments was decreased to not more than 1.0% by means of a hot roller type dried kept at 135° C. The dried filaments were subjected to a secondary drawing at 115° C. under wet heat to draw the filaments to 2 times their original length and then mechanically crimped, and the crimps were set to obtain 3-denier fibers.

The resulting fiber was a somewhat dull porous acrylic fiber having voids and having a porosity V of 0.3 cm³ /g and a surface area A of voids of 1.03 m² /g, the ratio V/A being 1/3.43. The porous acrylic fiber had the following yarn properties; that is, a fineness of 2 deniers, a strength in dried state of 2.9 g/d and an elongation in dried state of 30.5%. Further, the fiber had a strength in wet state of 2.87 g/d and an elongation in wet state of 31.3%. Therefore, the yarn property of the fiber in the dried state was maintained in the wet state.

EXAMPLE 9

A polymer mixture consisting of (100-X) parts of an acrylic polymer, which had a composition of AN:MA:SMAS=90.5:9.0:0.5(%), and X parts of cellulose acetate was dissolved in DMF to prepare a spinning solution containing 23% of the polymer mixture. The spinning solution was extruded from a spinneret into a coagulation bath consisting of 65% of DMF and 35% of water and kept at 20° C. The extruded filaments were subjected to a primary drawing to draw the filaments to 5 times their original length, and the primarily drawn filaments were washed with water and dried until the water content of the filaments was decreased to 0.5% by means of a hot roller type drier kept at 120° C. The dried filaments were then subjected to a secondary drawing at 110° C. under wet heat to draw the filaments to 1.2 times their original length and then mechanically crimped, and the crimps were set to obtain 2-denier fibers.

For comparison, in Experiment No. 98, the above described polymer mixture was dissolved in DMF to prepare a spinning solution containing 23% of the polymer mixture, and the spinning solution was extruded from a spinneret into a coagulation bath consisting of 65% of DMF and 35% of water and kept at 40° C. The extruded filaments were subjected to a primary drawing to draw the filaments to 6 times their original length, and the primarily drawn filaments were washed with water, subjected to a heat treatment at 125° C. under wet heat without drawing and shrinking, and then dried. The dried filaments were mechanically crimped, and the crimps were set to obtain 2-denier fibers. In experiment No. 99, the above described acrylic polymer alone was dissolved in DMF to prepare a spinning solution containing 23% of the acrylic polymer alone, and the spinning solution was extruded from a spinneret into a coagulation bath consisting of 65% of DMF and 35% of water and kept at 40° C. The extruded filaments were subjected to a primary drawing to draw the filaments to 5 times their original length, and the primarily drawn filaments were washed with water, subjected to a secondary drawing at 110° C. under wet heat to draw the filaments to 1.2 times their original length, and then dried in the same manner as described above. The dried filaments were mechanically crimped and the crimps were set to obtain 2-denier fibers.

Properties of the fibers are shown in the following Table 8. The dyeability (depth and brilliancy) was evaluated by the depth of color when a black dye was deposited on the fiber in an amount of 4.5% based on the amount of the fiber. In the evaluation of the dyeability, the depth of color of commercially available acrylic fiber (Kanebo Acryl Regular type) is graded as 5th grade. The larger the value, the more the sample fiber has a deeper and more brilliant color.

                                      TABLE 8                                      __________________________________________________________________________          Polymer                     Dyeability                                    Experi-                                                                             mixture                                                                             Ratio of                                                                             Water Yarn property                                                                             (depth and                                    ment X    microvoid                                                                            absorption                                                                           Strength                                                                            Elongation                                                                           brilliancy)                                   number                                                                              (parts)                                                                             (%)   (%)   (g/d)                                                                               (%)   (grade)                                                                               Remarks                                __________________________________________________________________________     95   4    10.2  21    3.6  39    4      Present                                                                        invention                              96   10   12.4  38    3.2  36    4      Present                                                                        invention                              97   15   16.0  43    3.0  33    3 ˜ 4                                                                           Present                                                                        invention                              98   4    78.6  24    2.2  26    1 ˜ 2                                                                           Comparative                                                                    sample                                 99   0    44.9   9    2.5  32    2      Comparative                                                                    sample                                 __________________________________________________________________________

EXAMPLE 10

A polymer mixture consisting of 85 parts of an acrylic polymer (I), which had a composition of AN:MA:SMAS=90.5:9.0:0.5(%), 15 parts of cellulose acetate (II), and a variable amount of an acrylic copolymer (III), which had a composition of AN:CH₂ =CH--COO--(CH₂ CH₂ O)₉ CH₃ =85:15(%), was dissolved in DMF to prepare a spinning solution containing 23% of the polymer mixture. The spinning solution was extruded from a spinneret into a coagulation bath consisting of 56% of DMF and 44% of water and kept at 20° C., and the extruded filaments were subjected to a primary drawing to draw the filaments to 5 times their original length. The primarily drawn filaments were dried until the water content in the filaments was decreased to 0.7% by means of a hot roller type drier kept at 120° C., and then subjected to a secondary drawing at 100° C. under wet heat to draw the filaments to 1.1 times their original length. The filaments were mechanically crimped, and the crimps were set to obtain 3-denier fibers. Properties of the fibers are shown in the following Table 9.

                                      TABLE 9                                      __________________________________________________________________________                                     Fiber property                                                  Void           Water                                          Experi-                                                                             Polymer mixture                                                                            Porosity,                                                                            Surface  absorp-                                        ment parts       V     area, A  tion                                           number                                                                              [I]                                                                               [II]                                                                               [III]                                                                               (cm.sup.3 /g)                                                                        (m.sup.2 /g)                                                                        V/A (%)  Others     Remarks                        __________________________________________________________________________     100  85 15  0.5  0.41  2.01                                                                                 ##STR95##                                                                         43   good in luster and in                                                                     Present invention              101  "  "   2    0.40  1.97                                                                                 ##STR96##                                                                         43   good in luster and in                                                                     Present invention              102  "  "   5    0.39  1.95                                                                                 ##STR97##                                                                         40   good in luster and in                                                                     Present invention              103  "  "   10   0.34  1.96                                                                                 ##STR98##                                                                         36   good in luster and in                                                                     Present invention              104  "  "   30   0.26  1.74                                                                                 ##STR99##                                                                         29   good in luster and in                                                                     Present invention              105  "  "   50   0.16  1.03                                                                                 ##STR100##                                                                        17   good in luster and in                                                                     Present invention              106  "  "   60   0.03  0.36                                                                                 ##STR101##                                                                         5   poor heat resistance                                                                      Comparative sample             __________________________________________________________________________

EXAMPLE 11

A polymer mixture consisting of 85 parts of an acrylic polymer (I), which had a composition of AN:MA:SAS=90.3:9.0:0.7(%), 15 parts of cellulose acetate (II) and 2 parts of an acrylic copolymer (III), which was a copolymer of 90% of AN and 10% of a monomer shown by the following general formula, was dissolved in DMF to prepare a spinning solution containing 27% of the polymer mixture. The extrusion of the spinning solution, and the after-treatment of the extruded filaments were carried out under the same condition as described in Example 10 to obtain 3-denier fibers.

The general formula of the above described monomer is as follows:

    CH.sub.2 ═CH--COOX

wheren X represents R₂ or ##STR102## (R₂, R₃, l and m are shown in the following Table 10).

Properties of the resulting fibers are shown in Table 10.

                                      TABLE 10                                     __________________________________________________________________________                                 Fiber property                                                    Void         Water                                              Experi-        Porosity,                                                                           Surface absorp-                                            ment Monomer   V    area, A tion                                               number                                                                              R.sub.2                                                                          R.sub.3                                                                           l  m (cm.sup.3 /g)                                                                       (m.sup.2 /g)                                                                        V/A                                                                               (%) Others Remarks                                 __________________________________________________________________________     107  H -- -- --                                                                               0.34 1.51                                                                                 ##STR103##                                                                       35  good in luster and dyeability                                                         Present invention                       108  --                                                                               H  8   0                                                                               0.40 1.99                                                                                 ##STR104##                                                                       43  good in luster and dyeability                                                         Present invention                       109  --                                                                               H  0  15                                                                               0.42 2.10                                                                                 ##STR105##                                                                       44  good in luster and dyeability                                                         Present invention                       110  --                                                                               CH.sub.3                                                                          10 15                                                                               0.43 2.15                                                                                 ##STR106##                                                                       46  good in luster and dyeability                                                         Present invention                       111  --                                                                               H  20 20                                                                               0.45 2.17                                                                                 ##STR107##                                                                       48  good in luster and dyeability                                                         Present invention                       __________________________________________________________________________

EXAMPLE 12

A polymer mixture consisting of 90 parts of an acrylic polymer, which had a composition of AN:MA:SMAS=90.5:9.0:0.5(%), and 10 parts of cellulose acetate was dissolved in DMF to prepare a spinning solution containing 23% of the polymer mixture. The spinning solution was extruded for a spinneret into a coagulation bath consisting of 60% of DMF and 40% of water and kept at a temperature shown in the following Table 11, and then the extruded filaments were subjected to a primary drawing to draw the filaments to 5 times their original length. The primarily drawn filaments were washed with water, dried so that the water content of the filaments would be decreased to not more than 1%, and then subjected to a secondary drawing at 110° C. under wet heat to draw the filaments to 1.4 times their original length. The secondarily drawn filaments were mechanically crimped, and the crimps were set to obtain 2-denier fibers. Properties of the fibers are shown in the following Table 11.

The fiber of Experiment No. 114 had a porosity of 1.10 cm³ /g before drying, a porosity of 0.213 cm³ /g after drying (before secondary drawing), and a porosity of 0.336 cm³ /g after secondary drawing.

                                      TABLE 11                                     __________________________________________________________________________     Coagula-                                                                       tion            Fiber property                                                 bath            Water                                                                              Yarn property                                                                            Dyeability                                       Experi-                                                                             tempera-                                                                            Ratio of                                                                             absorp-  Elonga-                                                                             (depth and                                                                           Heat                                       ment ture microvoid                                                                            tion                                                                               Strength                                                                            tion brilliancy)                                                                          resist-                                    number                                                                              (°C.)                                                                        (%)   (%) (g/d)                                                                               (%)  (grade)                                                                              ance  Remarks                              __________________________________________________________________________     112  10   7.8   38  3.4  37   4     good  Present                                                                        invention                            113  15   7.7   35  3.3  39   4     good  Present                                                                        invention                            114  20   11.8  37  3.2  38   4     good  Present                                                                        invention                            115  25   15.7  39  3.2  37   3 ˜ 4                                                                          good  Present                                                                        invention                            116  30   19.3  41  3.1  34   3     good  Present                                                                        invention                            117  35   34.0  43  2.7  29   2     somewhat                                                                             Comparative                                                              poor  sample                               118  40   49.0  45  2.4  25   1 ˜  2                                                                         poor  Comparative                                                                    sample                               __________________________________________________________________________

EXAMPLE 13

A polymer component A consisting of (100-C) parts of an acrylic polymer, which had a composition of AN:MA:SMAS=90.6:9.0:0.4(%), and C parts of cellulose acetate was dissolved in DMF to prepare a spinning solution A containing 22% of the polymer component A. A polymer component B consisting of the same acrylic polymer as used in the polymer component A was dissolved in DMF to prepare a spinning solution B containing 22% of the polymer component B. The spinning solutions A and B were extruded in a conjugate ratio of 5/5 (weight ratio) from a spinneret designed for side-by-side conjugate spinning into a coagulation bath consisting of a 65% DMF aqueous solution kept at 20° C.

The extruded filaments were subjected to a primary drawing to draw the filaments to 6 times their original length. The primarily drawn filaments were dried by means of a hot roller type drier kept at 120° C. until the water content of the filaments was decreased to 0.7%, and then subjected to a secondary drawing at 100° C. under wet heat to draw the filaments to 1.1 times their original length. The secondarily drawn filaments were mechanically crimped, and the crimps were set to obtain 3-denier fibers. The resulting acrylic composite fibers had substantially no latent crimpability. Properties of the fibers are shown in the following Table 12.

                                      TABLE 12                                     __________________________________________________________________________     Polymer                                                                        compo-    Void      Fiber property                                             Experi-                                                                             nent A    Surface                                                                             Water                                                      ment C    Porosity                                                                            area absorp-                                                    number                                                                              (parts)                                                                             (cm.sup.3 /g)                                                                       (m.sup.2 /g)                                                                        tion (%)                                                                            Dyeability                                                                           Others      Remarks                             __________________________________________________________________________     119   0   0.00 0.00  4   good  good luster Comparative                                                                    sample                              120   1   0.021                                                                               0.28  6   good  good luster Comparative                                                                    sample                              121   2   0.074                                                                               0.72 11   good  good luster Present                                                                        invention                           122   5   0.137                                                                               0.88 17   good  good luster Present                                                                        invention                           123  10   0.221                                                                               1.02 25   good  good luster Present                                                                        invention                           124  20   0.305                                                                               1.22 33   good  good luster Present                                                                        invention                           125  40   0.609                                                                               1.58 62   good  good luster Present                                                                        invention                           126  50   0.714                                                                               1.83 72   somewhat                                                                             good luster Present                                                      poor              invention                           127  60   0.924                                                                               2.16 92   poor  poor yarn property and                                                                     Comparative                                                        somewhat poor luster                                                                       sample                              __________________________________________________________________________

EXAMPLE 14

A polymer component A consisting of (100-C) parts of an acrylic polymer, which had a composition of AN:AM:SMAS=90.6:9.0:0.4(%), and C parts of cellulose acetate was dissolved in DMF to prepare a spinning solution A containing 22% of the polymer component A. A polymer component B consisting of an acrylic polymer having a composition of AN:MA:SMAS=90.4:9.0:0.6(%) was dissolved in DMF to prepare a spinning solution B containing 22% of the polymer component B. The spinning solutions A and B were extruded in various conjugate ratios from a spinneret, which was designed for bonding the spinning solutions A and B in a side-by-side relation, into a coagulation bath consisting of a 65% DMF aqueous solution kept at 20° C. Then, the extruded filaments were subjected to after-treatments in the same manner as described in Example 13 to obtain 3-denier acrylic composite fibers. Properties of the composite fibers are shown in the following Table 13. The resulting composite fibers had substantially no latent crimpability.

                                      TABLE 13(a)                                  __________________________________________________________________________     Polymer   Conjugate                                                            compo-    ratio of                                                                             Void      Fiber property                                       Experi-                                                                             nent A                                                                              A/B        Surface                                                                             Water                                                ment C    (weight                                                                              Porosity                                                                            area Absorp-                                              number                                                                              (parts)                                                                             ratio)                                                                               (cm.sup.3 /g)                                                                       (m.sup.2 /g)                                                                        tion (%)                                                                            Dyeability                                                                           Others     Remarks                        __________________________________________________________________________     128  2    1/9   0.01 0.17  4   good  poor water absorption                                                                     Comparative                                                                    sample                         129  2    2/8   0.03 0.33  6   good  somewhat poor water                                                                       Present                                                             absorption invention                      130  2    3/7   0.04 0.49  7   good  somewhat poor water                                                                       Present                                                             absorption invention                      131  2    5/5   0.06 0.81 12   good             Present                                                                        invention                      132  2    7/3   0.09 0.93 12   good             Present                                                                        invention                      133  2    8/2   0.10 1.07 13   good             Present                                                                        invention                      134  2    9/1   0.12 1.46 14   somewhat         Comparative                                                   poor             sample                         135  10   1/9   0.03 0.21  4   good  poor water absorption                                                                     Comparative                                                                    sample                         136  10   2/8   0.07 0.41 13   good             Present                                                                        invention                      137  10   3/7   0.13 0.63 17   good             Present                                                                        invention                      138  10   5/5   0.24 1.02 27   good             Present                                                                        invention                      __________________________________________________________________________

                                      TABLE 13(b)                                  __________________________________________________________________________     Polymer   Conjugate                                                            compo-    ratio of                                                                             Void      Fiber property                                       Experi-                                                                             nent A                                                                              A/B        Surface                                                                             Water                                                ment C    (weight                                                                              Porosity                                                                            area Absorp-                                              number                                                                              (parts)                                                                             ratio)                                                                               (cm.sup.3 /g)                                                                       (m.sup.2 /g)                                                                        tion (%)                                                                            Dyeability                                                                           Others     Remarks                        __________________________________________________________________________     139  10   6/4   0.25 1.22 28   good             Present                                                                        invention                      140  10   7/3   0.29 1.44 32   good             Present                                                                        invention                      141  10   8/2   0.32 1.63 35   somewhat                                                                             somewhat poor luster                                                                      Present                                                       poor             invention                      142  10   9/1   0.38 1.84 41   poor  poor luster                                                                               Comparative                                                                    sample                         143  30   1/9   0.06 0.28  7   good  poor water absorption                                                                     Comparative                                                                    sample                         144  30   2/8   0.12 0.54 14   good             Present                                                                        invention                      145  30   3/7   0.18 0.83 21   good             Present                                                                        invention                      146  30   5/5   0.24 1.39 33   good             Present                                                                        invention                      147  30   6/4   0.35 1.68 39   good             Present                                                                        invention                      148  30   7/3   0.41 1.91 42   somewhat                                                                             somewhat poor luster                                                                      Present                                                       poor             invention                      149  30   8/2   0.47 2.20 49   somewhat                                                                             somewhat poor luster                                                                      Present                                                       poor             invention                      __________________________________________________________________________

                                      TABLE 13(c)                                  __________________________________________________________________________     Polymer   Conjugate                                                            compo-    ratio of                                                                             Void      Fiber property                                       Experi-                                                                             nent A                                                                              A/B        Surface                                                                             Water                                                ment C    (weight                                                                              Porosity                                                                            area Absorp-                                              number                                                                              (parts)                                                                             ratio)                                                                               (cm.sup.3 /g)                                                                       (m.sup.2 /g)                                                                        (%)  Dyeability                                                                           Others     Remarks                        __________________________________________________________________________     150  30   9/1   0.53 2.48 54   poor  poor luster                                                                               Comparative                                                                    sample                         151  50   1/9   0.04 0.31 10   good  poor water absorption                                                                     Comparative                                                                    sample                         152  50   2/8   0.24 0.74 27   good             Present                                                                        invention                      153  50   3/7   0.39 1.12 43   good             Present                                                                        invention                      154  50   5/5   0.68 1.86 71   good             Present                                                                        invention                      155  50   6/4   0.79 2.23 85   somewhat                                                                             somewhat poor luster                                                                      Comparative                                                   poor             sample                         156  50   7/3   0.97 2.61 97   somewhat                                                                             poor in luster and                                                                        Comparative                                                   poor  in yarn property                                                                          sample                         157  50   8/2   1.07 2.98 110  poor  poor in luster and                                                                        Comparative                                                         in yarn property                                                                          sample                         158  50   9/1   1.21 3.38 126  poor  poor in luster and                                                                        Comparative                                                         in yarn property                                                                          sample                         __________________________________________________________________________

EXAMPLE 15

A polymer component A consisting of 85 parts of an acrylic polymer, which had a composition of AN:MA:SMAS=90.4:9.0:0.6(%), and 15 parts of cellulose acetate was dissolved in DMF to prepare a spinning solution A containing 22% of the polymer component A. A polymer component B consisting of the same acrylic polymer as used in the polymer component A was dissolved in DMF to prepare a spinning solution B containing 22% of the polymer component B. The spinning solutions A and B were extruded from a spinneret in a side-by-side relation and in a conjugate ratio (weight ratio) of component A/component B of 5/5 into a coagulation bath consisting of 60% of DMF and 40% of water and kept at a temperature shown in the following Table 14. The extruded filaments were subjected to a primary drawing to draw the filaments to 5 times their original length. Then, the primarily drawn filaments were washed with water, dried by means of a hot roller type drier kept at 120° C. until the water content of the filaments was decreased to not more than 1%, and then subjected to a secondary drawing at 110° C. under wet heat to draw the filaments to 1.2 times their original length. The secondarily drawn filaments were mechanically crimped and the crimps were set to obtain 2-denier composite fibers. Properties of the fibers are shown in Table 14. The evaluation of the dyeability was carried out in the same manner as described in Example 9.

                                      TABLE 14                                     __________________________________________________________________________                       Fiber property                                                    Coagulation                  Dyeability                                   Experi-                                                                             bath   Ratio of                                                                             Water                                                                               Yarn property                                                                             (depth and                                   ment temperature                                                                           microvoid                                                                            absorp-                                                                             Strength                                                                            Elongation                                                                           brilliancy)                                  number                                                                              (°C.)                                                                          (%)   tion (%)                                                                            (g/d)                                                                               (%)   (grade)                                                                              Remarks                                __________________________________________________________________________     159  10     7.4   27   3.5  41    4 ˜ 5                                                                          Present                                                                        invention                              160  15     7.2   27   3.3  39    4     Present                                                                        invention                              161  20     11.3  29   3.4  38    4     Present                                                                        invention                              162  25     15.1  30   3.2  34    4     Present                                                                        invention                              163  30     19.7  31   3.0  33    3 ˜ 4                                                                          Present                                                                        invention                              164  35     35.6  33   2.6  28    2     Comparative                                                                    sample                                 165  40     51.2  32   2.4  28    2     Comparative                                                                    sample                                 __________________________________________________________________________

EXAMPLE 16

A polymer component A consisting of 80 parts of an acrylic polymer, which had a composition of AN:MA:SMAS=91.5:8.0:0.5(%), and 20 parts of cellulose acetate and a polymer component B consisting of an acrylic polymer, which had a composition of AN:MA:SMAS=89.0:10.5:0.5(%), were separately dissolved in DMF to prepare spinning solutions A and B containing 23% of the polymer components A and B, respectively. The spinning solutions A and B were extruded from a spinneret in a conjugate ratio (weight ratio) of component A/component B of 5/5 and in a side-by-side relation into a coagulation bath consisting of a 56% DMF aqueous solution kept at 20° C. The extruded filaments were subjected to a primary drawing in a draw ratio shown in the following Table 15. The primarily drawn filaments were washed with water, dried by means of a hot roller type drier kept at 125° C. until the water content of the filaments were decreased to 0.7%, and then subjected to a secondary drawing at 115° C. under wet heat to draw the filaments to 1.4 times their original length. The secondarily drawn filaments were mechanically crimped, and the crimps were set to obtain a composite fiber having latent crimpability. Properties of the resulting composite fibers are shown in Table 15.

                                      TABLE 15                                     __________________________________________________________________________     Draw      Fiber property                                                       Experi-                                                                             ratio in                                                                            Water                                                                ment primary                                                                             absorp-                                                              number                                                                              drawing                                                                             tion (%)                                                                            Dyeability                                                                             Others Operability Remarks                              __________________________________________________________________________     166  2    39.7 poor    whitening                                                                             yarn breakage occurs                                                                       Comparative                                                        often after drying                                                                         sample                               167  2.5  39.4 substantially                                                                          somewhat           Present                                             good    whitening          invention                            168  3    37.5 good    good yarn                                                                             good crimp developing                                                                      Present                                                     property                                                                              property    invention                            169  4    35.6 good    good yarn                                                                             good crimp developing                                                                      Present                                                     property                                                                              property    invention                            170  6    36.7 good    good yarn                                                                             good crimp developing                                                                      Present                                                     property                                                                              property    invention                            171  8    35.3 good    good yarn                                                                             good crimp developing                                                                      Present                                                     property                                                                              property    invention                            172  9    24.7 good    good yarn                                                                             yarn breakage occurs                                                                       Comparative                                                 property                                                                              often during the                                                                           sample                                                             primary drawing                                  173  10   16.5 somewhat poor                                                                          uneven luster                                                                         yarn breakage occurs                                                                       Comparative                                                        often during the                                                                           sample                                                             primary drawing                                  __________________________________________________________________________

EXAMPLE 17

A polymer component A consisting of 70 parts of an acrylic polymer, which had a composition of AN:MA:SMAS=90.6:9.0:0.4(%), and 30 parts of cellulose acetate, and a polymer component B consisting of the same acrylic polymer as used in the polymer component A, which had a composition of AN:MA:SMAS=90.6:9.0:0.4(%), was dissolved in DMF to prepare spinning solutions A and B containing 25% of the polymer components A and B, respectively. The spinning solutions A and B were extruded from a spinneret in a conjugate ratio (weight ratio) of component A/component B of 5/5 and in a side-by-side relation into a coagulation bath consisting of a 60% DMF aqueous solution kept at 25° C. The extruded filaments were subjected to a primary drawing to draw the filaments to 4 times their original length. The primarily drawn filaments were washed with water, dried by means of a hot roller type drier kept at a temperature shown in the following Table 16 until the water content of the filaments was decreased to not more than 0.8%, and then subjected to a secondary drawing at 105° C. under wet heat to draw the filaments to 1.6 times their original length. The secondarily drawn filaments were mechanically crimped, and the crimps were set to obtain 3-denier composite fibers. Properties of the fibers are shown in Table 16.

                                      TABLE 16                                     __________________________________________________________________________                 Void      Fiber property                                           Experi-                                                                             Drying      Surface                                                                             Water                                                    ment temperature                                                                           Porosity                                                                            area absorp-                                                  number                                                                              (°C.)                                                                          (cm.sup.3 /g)                                                                       (m.sup.2 /g)                                                                        tion (%)                                                                            Dyeability                                                                           Others     Remarks                            __________________________________________________________________________     174   60    0.56 19.4 58   poor  yarn property is poor                                                                     Comparative                                                         and fiber is whitened                                                                     sample                             175   80    0.51 16.3 53   poor  yarn property is poor                                                                     Comparative                                                         and fiber is whitened                                                                     sample                             176  100    0.46 6.88 49   somewhat         Present                                                       poor             invention                          177  120    0.42 1.57 46   good             Present                                                                        invention                          178  140    0.37 1.43 40   good             Present                                                                        invention                          179  160    0.31 1.36 34   good             Present                                                                        invention                          180  180    0.26 1.14 27   good  fiber somewhat colors                                                                     Present                                                                        invention                          181  190    0.21 1.05 24   good  fiber colors and                                                                          Comparative                                                         becomes rigid                                                                             sample                             182  200    0.18 0.91 22   somewhat                                                                             fiber colors and                                                                          Comparative                                                   poor  becomes rigid                                                                             sample                             __________________________________________________________________________

EXAMPLE 18

The same water washed filament tows as those obtained in Example 17, which had been swollen with water, were dried by means of a hot roller type drier kept at 120° C. until the water content of the tows were decreased to various water contents shown in the following Table 17, and the dried tows were treated under the same after-treatment condition as described in Example 17 to obtain 3-denier fibers. Properties of the fibers are shown in Table 17.

                                      TABLE 17                                     __________________________________________________________________________              Void      Fiber property                                              Experi-                                                                             Water    Surface                                                                             Water                                                       ment content                                                                            Porosity                                                                            area absorp-                                                     number                                                                              (%) (cm.sup.3 /g)                                                                       (m.sup.2 /g)                                                                        tion (%)                                                                            Dyeability                                                                           Others     Remarks                               __________________________________________________________________________     183  0.1 0.37 1.28 40   good             Present                                                                        invention                             184  0.3 0.39 1.41 42   good             Present                                                                        invention                             185  0.5 0.38 1.34 41   good             Present                                                                        invention                             186  0.7 0.41 1.49 43   good             Present                                                                        invention                             187  1.0 0.43 2.48 45   good             Present                                                                        invention                             188  1.1 0.53 5.69 54   somewhat                                                                             uneven luster and                                                                         Comparative                                                   poor  uneven yarn property                                                                      sample                                189  1.5 0.76 13.7 78   poor  uneven luster and                                                                         Comparative                                                         uneven yarn property                                                                      sample                                190  2.0 0.89 16.4 89   poor  uneven luster and                                                                         Comparative                                                         uneven yarn property                                                                      sample                                191  5.0 1.30 23.1 126  poor  uneven luster and                                                                         Comparative                                                         uneven yarn property                                                                      sample                                __________________________________________________________________________

EXAMPLE 19

A polymer component A consisting of 70 parts of an acrylic polymer, which had a composition of AN:MA:SMAS=92.5:7.0:0.5(%), and 30 parts of cellulose acetate, and a polymer component B consisting of an acrylic polymer, which had a composition of AN:MA:SMAS=90.5:9.0:0.5(%), were separately dissolved in DMF to prepare spinning solutions A and B containing 25% of the polymer components A and B, respectively. The spinning solutions A and B were extruded from a spinneret in a conjugate ratio (weight ratio) of component A/component B of 5/5 and in a side-by-side relation into a coagulation bath consisting of a 60% DMF aqueous solution kept at 18° C. The extruded filaments were subjected to a primary drawing to draw the filaments to 5 times their original length. The primarily drawn filaments were washed with water, dried by means of a hot roller type drier kept at 120° C. while blowing hot air kept at 130° C. until the water content of the filaments was decreased to 0.7%, and then subjected to a secondary drawing under a condition shown in the following Table 18. The secondarily drawn filaments were mechanically crimped, and the crimps were set to obtain composite fibers having a latent crimpability. Properties of the fibers are shown in Table 18.

                                      TABLE 18(a)                                  __________________________________________________________________________     Secondary                                                                      drawing condition                                                                            Fiber property                                                   Experi-                                                                             Tempera- Water                                                            ment ture Draw                                                                               absorp-                                                          number                                                                              (°C.)                                                                        ratio                                                                              tion (%)                                                                            Dyeability                                                                           Others   Operability                                                                              Remarks                            __________________________________________________________________________     192  100  0.9 39   good  good luster                                                                             good      Present                                                                        invention                          193  100  1.0 43   good  good luster                                                                             good      Present                                                                        invention                          194  100  1.5 41   good  good luster                                                                             good      Present                                                                        invention                          195  100  2   36   good  good luster                                                                             good      Present                                                                        invention                          196  100  3   31   somewhat                                                                             somewhat poor in                                                                        some yarn breakage                                                                       Present                                               poor  luster and in      invention                                                   yarn property                                         197  110  0.9 44   good  good luster                                                                             good      Present                                                                        invention                          198  110  1.0 45   good  good luster                                                                             good      Present                                                                        invention                          199  110  1.5 41   good  good luster                                                                             good      Present                                                                        invention                          __________________________________________________________________________

                                      TABLE 18(b)                                  __________________________________________________________________________     Secondary                                                                      drawing condition                                                                            Fiber property                                                   Experi-                                                                             Tempera- Water                                                            ment ture Draw                                                                               absorp-                                                          number                                                                              (°C.)                                                                        ratio                                                                              tion (%)                                                                            Dyeability                                                                           Others   Operability                                                                              Remarks                            __________________________________________________________________________     200  110  2   38   good  good luster                                                                             good      Present                                                                        invention                          201  110  3   31   somewhat                                                                             somewhat poor in                                                                        some yarn breakage                                                                       Present                                               poor  luster and in      invention                                                   yarn property                                         202  110  4   --    --    --      frequent yarn                                                                            Comparative                                                          breakage and poor                                                                        sample                                                               operability                                  203  120  0.85                                                                               35   good  good luster                                                                             good      Present                                                                        invention                          204  120  1.0 41   good  good luster                                                                             good      Present                                                                        invention                          205  120  2   36   good  good luster                                                                             good      Present                                                                        invention                          __________________________________________________________________________

                                      TABLE 18(c)                                  __________________________________________________________________________     Secondary                                                                      drawing condition                                                                            Fiber property                                                   Experi-                                                                             Tempera- Water                                                            ment ture Draw                                                                               absorp-                                                          number                                                                              (°C.)                                                                        ratio                                                                              tion (%)                                                                            Dyeability                                                                           Others   Operability                                                                              Remarks                            __________________________________________________________________________     206  120  3   29   somewhat                                                                             somewhat poor in                                                                        some yarn breakage                                                                       Present                                               poor  luster and in      invention                                                   yarn property                                         207  120  4   18   somewhat                                                                             somewhat poor in                                                                        frequent yarn                                                                            Comparative                                           poor  luster and in                                                                           breakage  sample                                                      yarn property                                         208  130  0.8 33   good  good luster                                                                             good      Present                                                                        invention                          209  130  1.0 35   good  good luster                                                                             good      Present                                                                        invention                          210  130  2   31   good  good luster                                                                             good      Present                                                                        invention                          211  130  3   25   somewhat                                                                             somewhat poor in                                                                        some yarn breakage                                                                       Present                                               poor  luster and in      invention                                                   yarn property                                         212  130  4   16   somewhat                                                                             somewhat poor in                                                                        frequent yarn                                                                            Comparative                                           poor  luster and in                                                                           breakage  sample                                                      yarn property                                         __________________________________________________________________________

EXAMPLE 20

A polymer component A consisting of (100-C) parts of an acrylic polymer, which had a composition of AN:MA:SMAS=(99.5-x):x:0.5(%), and C parts of cellulose acetate, and a polymer component B consisting of an acrylic polymer, which had a composition of AN:MA:SMAS=(99.5-y):y:0.5(%), were separately dissolved in DMF to prepare spinning solutions A and B containing 23% of the polymer components A and B, respectively. The spinning solutions A and B were extruded from a spinneret in a conjugate ratio (weight ratio) of component A/component B of 5/5 and in a side-by-side relation into a coagulation bath consisting of a 56% DMF aqueous solution kept at 15° C. The extruded filaments were subjected to a primary drawing to draw the filaments to 4 times their original length. The primarily drawn filaments were washed with water, dried by means of a hot roller type drier kept at 125° C. until the water content of the filaments was decreased to 0.5%, and subjected to a secondary drawing at 115° C. under wet heat to draw the filaments to 1.3 times their original length, and the secondarily drawn filaments were subjected to a primary shrinking at 130° C. under wet heat to shrink the filaments to 0.9 time their original length.

Then, in order to improve the crimpability of the filaments, the above treated filaments were further subjected to a tertiary drawing at 180° C. under dry heat to draw the filaments to 1.4 times their original length, and the above drawn filaments were subjected to a secondary shrinking at 150° C. under dry heat to shrink the filaments to 0.9 times their original length. Then, the above treated filaments were mechanically crimped, and the crimps were set to obtain 3-denier composite fibers having a latent crimpability. The composite fiber obtained in the present invention has substantially the same crimpability as that of comparative sample and further has improved dyeability and water-absorbing property. Properties of the above obtained fibers are shown in the following Table 19.

                                      TABLE 19                                     __________________________________________________________________________     Polymer component  Fiber property                                              Experi-                                                                             Component A                                                                           Component B                                                                           Water                                                       ment x  C   y      absorption                                                  number                                                                              (%)                                                                               (parts)                                                                            (%)    (%)   Dyeability                                                                           Crimpability                                                                          Remarks                                  __________________________________________________________________________     213   7 10  9      24    good  good   Present                                                                        invention                                214   7 20  9      31    good  good   Present                                                                        invention                                215   7 30  9      35    good  good   Present                                                                        invention                                216  10 10  8      21    good  good   Present                                                                        invention                                217  10 20  8      29    good  good   Present                                                                        invention                                218  10 30  8      34    good  good   Present                                                                        invention                                219   7  0  9       4    good  good   Comparative                                                                    sample                                   220  10  0  8       4    good  good   Comparative                                                                    sample                                   __________________________________________________________________________

EXAMPLE 21

A polymer component A consisting of 70 parts of an acrylic polymer, which had a composition of AN:MA:SMAS=91.5:8.0:0.5(%), 30 parts of cellulose acetate and 10 parts of an acrylic copolymer having a composition of AN:CH₂ =CHCOO--CH₂ CH₂ O)₂₀ H=90:10(%), and a component polymer B consisting of an acrylic polymer, which had a composition of AN:MA:SMAS=89.5:10.0:0.5(%), were separately dissolved in DMF to prepare spinning solutions A and B containing 23% of the polymer components A and B, respectively. The spinning solutions A and B were conjugate spun in a conjugate ratio (weight ratio) of component A/component B of 5/5. The spinning and the after-treatment were effected under the same spinning and after-treatment conditions as described in Example 20 to obtain 3-denier composite fibers having a latent crimpability.

The resulting composite fiber had a porosity of 0.20 cm³ /g, a surface area of voids of 1.13 m² /g and a water absorption of 27%. In the fiber, crimps were able to be easily developed by treating the fibers with boiling water at 100° C. for 5 minutes. The crimped fiber had a strength of 2.7 g/d, an elongation of 32.3%, a number of crimps of 32 per inch of fiber, a percentage crimp of 46%, an elastic recovery of crimp of 74% and a residual percentage crimp of 34%, and further had an excellent bulkiness.

EXAMPLE 22

A polymer component A consisting of (100-C₁) parts of an acrylic polymer, which had a composition of AN:MA:SMAS=92.4:7.0:0.6(%), and C₁ parts of cellulose acetate was dissolved in DMF to prepare a spinning solution A consisting of 23% of the polymer component A. A polymer component B consisting of (100-C₂) parts of an acrylic polymer, which had a composition of AN:MA:SMAS=90.4:9.0:0.6(%), and C₂ parts of cellulose acetate was dissolved in DMF to prepare a spinning solution B containing 23% of the polymer component B. The spinning solutions A and B were extruded from a spinneret in a conjugate ratio of component A/component B of 1:1 and in a side-by-side relation into a coagulation bath consisting of a 56% DMF aqueous solution kept at 16° C. The extruded filaments were subjected to a primary drawing to draw the filaments to 4 times their original length, washed with water and then dried by means of a hot roller type drier kept at 125° C. until the water content of the filaments was decreased to 0.7%. The dried filaments were subjected to a secondary drawing at 110° C. under wet heat to draw the filaments to 1.6 times their original length, the secondarily drawn filaments were subjected to a primary shrinking at 125° C. under wet heat to shrink the filaments to 0.9 time their original length, the primarily shrunk filaments were subjected to a tertiary drawing at 180° C. under dry heat to draw the filaments to 1.4 times their original length, and then the drawn filaments were subjected to a secondary shrinking at 150° C. under dry heat to shrink the filaments to 0.9 times their original length. The above treated filaments were mechanically crimped and the crimps were set to obtain composite fibers having a latent crimpability. Properties of the composite fibers are shown in the following Table 20.

                                      TABLE 20(a)                                  __________________________________________________________________________                    Void      Fiber property                                        Experi-                                                                             Polymer component                                                                             Surface                                                                             Water                                                 ment C.sub.1                                                                             C.sub.2                                                                             Porosity                                                                            area absorp-                                               number                                                                              (parts)                                                                             (parts)                                                                             (cm.sup.3 /g)                                                                       (m.sup.2 /g)                                                                        tion (%)                                                                            Dyeability                                                                           Others   Remarks                           __________________________________________________________________________     221  2     2   0.105                                                                               1.35 14   good           Present                                                                        invention                         222  2    10   0.231                                                                               1.62 26   good           Present                                                                        invention                         223  2    20   0.294                                                                               1.84 33   good           Present                                                                        invention                         224  2    30   0.357                                                                               2.01 38   good           Present                                                                        invention                         225  2    50   0.731                                                                               2.56 77   somewhat                                                                             somewhat poor                                                                           Present                                                         poor  in strength and                                                                         invention                                                             in elongation                              226  2    60   0.945                                                                               2.94 94   poor  poor in strength                                                                        Comparative                                                           and in elongation                                                                       sample                            227  10     2  0.245                                                                               1.43 27   good           Present                                                                        invention                         228  10   10   0.357                                                                               1.76 38   good           Present                                                                        invention                         229  10   30   0.483                                                                               1.89 50   good           Present                                                                        invention                         __________________________________________________________________________

                                      TABLE 20(b)                                  __________________________________________________________________________                    Void      Fiber property                                        Experi-                                                                             Polymer component                                                                             Surface                                                                             Water                                                 ment C.sub.1                                                                             C.sub.2                                                                             Porosity                                                                            area absorp-                                               number                                                                              (parts)                                                                             (parts)                                                                             (cm.sup.3 /g)                                                                       (m.sup.2 /g)                                                                        tion (%)                                                                            Dyeability                                                                           Others   Remarks                           __________________________________________________________________________     230  10   50   0.851                                                                               1.91 84   somewhat                                                                             poor in strength                                                                        Comparative                                                     poor  and in elongation                                                                       sample                            231  30   10   0.473                                                                               1.94 49   good           Present                                                                        invention                         232  30   30   0.578                                                                               2.57 60   somewhat                                                                             somewhat poor                                                                           Present                                                         poor  in strength and                                                                         invention                                                             in elongation                              233  30   50   0.945                                                                               3.48 100  poor  poor in strength                                                                        Comparative                                                           and in elongation                                                                       sample                            234   2   10   0.231                                                                               1.62 25   good           Present                                                                        invention                         235  10   10   0.353                                                                               1.75 39   good           Present                                                                        invention                         236  30   10   0.476                                                                               1.94 51   good           Present                                                                        invention                         237  50   10   0.735                                                                               2.41 74   somewhat                                                                             somewhat poor                                                                           Present                                                         poor  in strength and                                                                         invention                                                             in elongation                              __________________________________________________________________________

                                      TABLE 20(c)                                  __________________________________________________________________________                    Void      Fiber property                                        Experi-                                                                             Polymer component                                                                             Surface                                                                             Water                                                 ment C.sub.1                                                                             C.sub.2                                                                             Porosity                                                                            area absorp-                                               number                                                                              (parts)                                                                             (parts)                                                                             (cm.sup.3 /g)                                                                       (m.sup.2 /g)                                                                        tion (%)                                                                            Dyeability                                                                           Others   Remarks                           __________________________________________________________________________     238  60   10   1.007                                                                               2.98 117  poor  poor in strength                                                                        Comparative                                                           and in elongation                                                                       sample                            239   2   30   0.315                                                                               1.88 33   good           Present                                                                        invention                         240  10   30   0.469                                                                               1.93 49   good           Present                                                                        invention                         241  30   30   0.563                                                                               2.57 58   somewhat                                                                             somewhat poor                                                                           Present                                                         poor  in strength and                                                                         invention                                                             in elongation                              242  50   30   0.913                                                                               3.49 92   poor  poor in strength                                                                        Comparative                                                           and in elongation                                                                       sample                            __________________________________________________________________________

EXAMPLE 23

A polymer component A consisting of (100-C₁) parts of an acrylic polymer, which had a composition of AN:MA:SMAS=92.4:7.0:0.6(%), and C₁ parts of cellulose acetate was dissolved in DMF to prepare a spinning solution A containing 23% of the polymer component A. A polymer component B consisting of (100-C₂) parts of an acrylic copolymer, which had a composition of AN:MA:SMAS=89.4:10.0:0.6(%), and C₂ parts of cellulose acetate was dissolved in DMF to prepare a spinning solution B containing 23% of the polymer component B. The spinning solutions A and B were extruded from a spinneret in various conjugate ratios (weight ratio of component A/component B) shown in the following Table 21 and in a side-by-side relation into a coagulation bath consisting of a 56% DMF aqueous solution kept at 16° C. The spinning, drawing and after-treatment were carried out under the same conditions as described in Example 22 to obtain 3-denier composite fibers having a latent crimpability. The fibers were treated in hot water kept at 100° C. for 5 minutes to develop crimps. Properties of the fibers are shown in Table 21.

                                      TABLE 21(a)                                  __________________________________________________________________________     Polymer                 Fiber property                                         Experi-                                                                             component                                                                              Conjugate                                                                            Void Water Number of                                        ment C.sub.1                                                                            C.sub.2                                                                            ratio Porosity                                                                            absorption                                                                           crimps/                                          number                                                                              (parts)                                                                            (parts)                                                                            A/B   (cm.sup.3 /g)                                                                       (%)   inch  Remarks                                    __________________________________________________________________________     243  2   28  8/2   0.205                                                                               23    11    Comparative                                                                    sample                                     244  2   28  7/3   0.221                                                                               25    23    Present                                                                        invention                                  245  2   28  6/4   0.293                                                                               33    44    Present                                                                        invention                                  246  2   28  5/5   0.339                                                                               35    52    Present                                                                        invention                                  247  2   28  4/6   0.374                                                                               39    48    Present                                                                        invention                                  248  2   28  3/7   0.416                                                                               44    29    Present                                                                        invention                                  249  2   28  2/8   0.473                                                                               49    13    Comparative                                                                    sample                                     250  7   23  8/2   0.320                                                                               35    14    Comparative                                                                    sample                                     251  7   23  7/3   0.343                                                                               34    25    Present                                                                        invention                                  252  7   23  6/4   0.364                                                                               38    48    Present                                                                        invention                                  253  7   23  5/5   0.381                                                                               41    61    Present                                                                        invention                                  254  7   23  4/6   0.409                                                                               43    50    Present                                                                        invention                                  255  7   23  3/7   0.429                                                                               45    31    Present                                                                        invention                                  __________________________________________________________________________

                                      TABLE 21(b)                                  __________________________________________________________________________     Polymer                 Fiber property                                         Experi-                                                                             component                                                                              Conjugate                                                                            Void Water Number of                                        ment C.sub.1                                                                            C.sub.2                                                                            ratio Porosity                                                                            absorption                                                                           crimps/                                          number                                                                              (parts)                                                                            (parts)                                                                            A/B   (cm.sup.3 /g)                                                                       (%)   inch  Remarks                                    __________________________________________________________________________     256   7  23  2/8   0.453                                                                               48    17    Comparative                                                                    sample                                     257  15  15  8/2   0.403                                                                               41    13    Comparative                                                                    sample                                     258  15  15  7/3   0.414                                                                               43    25    Present                                                                        invention                                  259  15  15  5/5   0.404                                                                               45    54    Present                                                                        invention                                  260  15  15  3/7   0.407                                                                               41    29    Present                                                                        invention                                  261  15  15  2/8   0.409                                                                               43    16    Comparative                                                                    sample                                     262  10  10  8/2   0.357                                                                               37    15    Comparative                                                                    sample                                     263  10  10  7/3   0.363                                                                               39    26    Present                                                                        invention                                  264  10  10  6/4   0.351                                                                               36    47    Present                                                                        invention                                  265  10  10  5/5   0.349                                                                               37    58    Present                                                                        invention                                  266  10  10  4/6   0.353                                                                               38    51    Present                                                                        invention                                  267  10  10  3/7   0.364                                                                               38    34    Present                                                                        invention                                  268  10  10  2/8   0.358                                                                               37    17    Comparative                                                                    sample                                     __________________________________________________________________________

EXAMPLE 24

A polymer component A consisting of 90 parts of an acrylic polymer, which had a composition of AN:(M-1):SMAS=(99.5-x):x:0.5(%), and 10 parts of cellulose acetate, and a polymer component B consisting of 90 parts of an acrylic copolymer, which had a composition of AN:(M-2):SMAS=(99.5-y):y:0.5(%), and 10 parts of cellulose acetate were separately dissolved in DMF to prepare spinning solutions A and B containing 25% of the polymer components A and B, respectively. The spinning solutions A and B were extruded from a spinneret in a conjugate ratio (weight ratio of component A/component B) of 5/5 and in a side-by-side relation into a coagulation bath consisting of a 56% DMF aqueous solution kept at 20° C. The extruded filaments were subjected to a primary drawing to draw the filaments to 5 times their original length, washed with water, and then dried by means of a hot roller type drier kept at 125° C. until the water content of the filaments was decreased to not more than 0.7%. After the drying, the dried filaments were treated under the same conditions as described in Example 22 to obtain 3-denier composite fibers having a latent crimpability. The fibers were treated in hot water kept at 100° C. for 5 minutes to develop crimps.

Properties of the fibers are shown in the following Table 22.

                                      TABLE 22(a)                                  __________________________________________________________________________                                     Fiber property                                 Polymer component               Water                                                                              Number                                     Experi-                                                                             Polymer A  Polymer B  Void absorp-                                                                            of                                         ment         x          y  Porosity                                                                            tion                                                                               crimps/                                                                             Crimp-                                number                                                                              M-1     (%)                                                                               M-2     (%)                                                                               (cm.sup.3 /g)                                                                       (%) inch ability                                                                            Remarks                           __________________________________________________________________________     269  methyl acrylate                                                                        5  methyl acrylate                                                                        6  0.347                                                                               36  13   poor                                                                               Comparative                                                                    sample                            270  methyl acrylate                                                                        5  methyl acrylate                                                                        6.5                                                                               0.349                                                                               37  16   poor                                                                               Comparative                                                                    sample                            271  methyl acrylate                                                                        5  methyl acrylate                                                                        7  0.351                                                                               37  34   high                                                                               Present                                                                        invention                         272  methyl acrylate                                                                        5  methyl acrylate                                                                        7.5                                                                               0.356                                                                               38  47   high                                                                               Present                                                                        invention                         273  methyl acrylate                                                                        5  methyl acrylate                                                                        8  0.371                                                                               40  53   high                                                                               Present                                                                        invention                         274  methyl acrylate                                                                        6  methyl acrylate                                                                        7  0.353                                                                               36  11   poor                                                                               Comparative                                                                    sample                            275  methyl acrylate                                                                        6  methyl acrylate                                                                        7.5                                                                               0.355                                                                               37  15   poor                                                                               Comparative                                                                    sample                            276  methyl acrylate                                                                        6  methyl acrylate                                                                        8  0.361                                                                               36  28   high                                                                               Present                                                                        invention                         277  methyl acrylate                                                                        6  methyl acrylate                                                                        8.5                                                                               0.367                                                                               39  39   high                                                                               Present                                                                        invention                         278  methyl acrylate                                                                        6  methyl acrylate                                                                        9  0.371                                                                               39  47   high                                                                               Present                                                                        invention                         __________________________________________________________________________

                                      TABLE 22(b)                                  __________________________________________________________________________                                     Fiber property                                 Polymer component               Water                                                                              Number                                     Experi-                                                                             Polymer A  Polymer B  Void absorp-                                                                            of                                         ment         x          y  Porosity                                                                            tion                                                                               crimps/                                                                             Crimp-                                number                                                                              M-1     (%)                                                                               M-2     (%)                                                                               (cm.sup.3 /g)                                                                       (%) inch ability                                                                            Remarks                           __________________________________________________________________________     279  methyl acrylate                                                                        7  methyl acrylate                                                                        8  0.357                                                                               38  12   poor                                                                               Comparative                                                                    sample                            280  methyl acrylate                                                                        7  methyl acrylate                                                                        8.5                                                                               0.363                                                                               38  17   poor                                                                               Comparative                                                                    sample                            281  methyl acrylate                                                                        7  methyl acrylate                                                                        9  0.361                                                                               38  31   high                                                                               Present                                                                        invention                         282  methyl acrylate                                                                        7  methyl acrylate                                                                        9.5                                                                               0.371                                                                               39  43   high                                                                               Present                                                                        invention                         283  methyl acrylate                                                                        7  methyl acrylate                                                                        10 0.365                                                                               38  54   high                                                                               Present                                                                        invention                         284  methyl acrylate                                                                        9  methyl acrylate                                                                        10.5                                                                              0.351                                                                               37  16   poor                                                                               Comparative                                                                    sample                            285  methyl acrylate                                                                        9  methyl acrylate                                                                        11 0.353                                                                               37  31   high                                                                               Present                                                                        invention                         286  methyl acrylate                                                                        9  methyl acrylate                                                                        12 0.347                                                                               36  45   high                                                                               Present                                                                        invention                         __________________________________________________________________________

                                      TABLE 22(c)                                  __________________________________________________________________________                                     Fiber property                                 Polymer component               Water                                                                              Number                                     Experi-                                                                             Polymer A  Polymer B  Void absorp-                                                                            of                                         ment         x          y  Porosity                                                                            tion                                                                               crimps/                                                                             Crimp-                                number                                                                              M-1     (%)                                                                               M-2     (%)                                                                               (cm.sup.3 /g)                                                                       (%) inch ability                                                                            Remarks                           __________________________________________________________________________     287  methyl acrylate                                                                        10 methyl acrylate                                                                        11.5                                                                              0.341                                                                               36  14   poor                                                                               Comparative                                                                    sample                            288  methyl acrylate                                                                        10 methyl acrylate                                                                        12 0.337                                                                               35  29   high                                                                               Present                                                                        invention                         289  methyl acrylate                                                                        10 methyl acrylate                                                                        13 0.329                                                                               34  41   high                                                                               Present                                                                        invention                         290  methyl acrylate                                                                        10 methyl acrylate                                                                        14 0.325                                                                               34  56   high                                                                               Present                                                                        invention                         291  vinyl acetate                                                                           9 vinyl acetate                                                                          10 0.374                                                                               39  11   poor                                                                               Comparative                                                                    sample                            292  vinyl acetate                                                                           9 vinyl acetate                                                                          10.5                                                                              0.377                                                                               41  17   poor                                                                               Comparative                                                                    sample                            293  vinyl acetate                                                                           9 vinyl acetate                                                                          11.0                                                                              0.383                                                                               40  28   high                                                                               Present                                                                        invention                         294  vinyl acetate                                                                           9 vinyl acetate                                                                          11.5                                                                              0.371                                                                               39  37   high                                                                               Present                                                                        invention                         295  vinyl acetate                                                                           9 vinyl acetate                                                                          12.0                                                                              0.363                                                                               38  49   high                                                                               Present                                                                        invention                         296  vinyl acetate                                                                           9 vinyl acetate                                                                          12.5                                                                              0.358                                                                               37  56   high                                                                               Present                                                                        invention                         __________________________________________________________________________

                                      TABLE 22(d)                                  __________________________________________________________________________                                       Fiber property                               Polymer component                 Water                                                                              Number                                   Experi-                                                                             Polymer A  Polymer B    Void absorp-                                                                            of                                       ment         x          y    Porosity                                                                            tion                                                                               crimps/                                                                             Crimp-                              number                                                                              M-1     (%)                                                                               M-2     (%)  (cm.sup.3 /g)                                                                       (%) inch ability                                                                            Remarks                         __________________________________________________________________________     297  a mixture of                                                                           8  a mixture of                                                                            9(2*)                                                                              0.293                                                                               31  12   poor                                                                               Comparative                          7% of methyl                                                                              7% of methyl                   Sample                               acrylate and                                                                              acrylate and                                                        1% of acryl-                                                                              acrylamide*                                                         amide                                                                     298  a mixture of                                                                           8  a mixture of                                                                            9.5(2.5)                                                                           0.279                                                                               30  19   poor                                                                               Comparative                          7% of methyl                                                                              7% of methyl                   Sample                               acrylate and                                                                              acrylate and                                                        1% of acryl-                                                                              acrylamide*                                                         amide                                                                     299  a mixture of                                                                           8  a mixture of                                                                           10 (3.0)                                                                            0.237                                                                               27  31   high                                                                               Present                              7% of methyl                                                                              7% of methyl                   invention                            acrylate and                                                                              acrylate and                                                        1% of acryl-                                                                              acrylamide*                                                         amide                                                                     300  a mixture of                                                                           8  a mixture of                                                                           10.5(3.5)                                                                           0.231                                                                               25  43   high                                                                               Present                              7% of methyl                                                                              7% of methyl                   invention                            acrylate and                                                                              acrylate and                                                        1% of acryl-                                                                              acrylamide*                                                         amide                                                                     301  a mixture of                                                                           8  a mixture of                                                                           11 (4.0)                                                                            0.245                                                                               26  51   high                                                                               Present                              7% of methyl                                                                              7% of methyl                   invention                            acrylate and                                                                              acrylate and                                                        1% of acryl-                                                                              acrylamide*                                                         amide                                                                     302  methyl acrylate                                                                        7  2-hydroxyethyl                                                                          9   0.349                                                                               37  13   poor                                                                               Comparative                                     methacrylate                   sample                          303  methyl acrylate                                                                        7  2-hydroxyethyl                                                                          9.5 0.353                                                                               38  17   poor                                                                               Comparative                                     methacrylate                   sample                          304  methyl acrylate                                                                        7  2-hydroxyethyl                                                                         10   0.358                                                                               39  28   high                                                                               Present                                         methacrylate                   invention                       305  methyl acrylate                                                                        7  2-hydroxyethyl                                                                         11   0.361                                                                               40  41   high                                                                               Present                                         methacrylate                   invention                       __________________________________________________________________________

EXAMPLE 25

A polymer component A consisting of 85 parts of an acrylic polymer, which had a composition of AN:MA:SMAS=90.6:9.0:0.4(%), and 15 parts of cellulose acetate, and a polymer component B consisting of 85 parts of an acrylic polymer, which had a composition of AN:MA:SMAS=87.5:12.0:0.5(%), and 15 parts of cellulose acetate were separately dissolved in DMF to prepare spinning solutions A and B containing 23% of the polymer components A and B, respectively. The spinning solutions A and B were extruded from a spinneret in a conjugate ratio (weight ratio), of component A:component B of 5:5 and in a side-by-side relation into a coagulation bath consisting of a 65% DMF aqueous solution kept at 15° C. The extruded filaments were subjected to a primary drawing under the condition shown in the following Table 23, and washed with water. Then, the filaments were dried and after-treated under the same conditions as described in Example 22 to obtain composite fibers having a latent crimpability. Properties of the fibers are shown in Table 23.

                                      TABLE 23                                     __________________________________________________________________________                         Fiber property                                             Draw      Void      Water                                                      Experi-                                                                             ratio in  Surface                                                                             absorp-                                                    ment primary                                                                             Porosity                                                                            area tion                                                                               Dye-                                                   number                                                                              drawing                                                                             (cm.sup.3 /g)                                                                       (m.sup.2 /g)                                                                        (%) ability                                                                              Others  Operability                                                                            Remarks                          __________________________________________________________________________     306  2    0.443                                                                               7.64 43  somewhat                                                                             somewhat poor                                                                          dried yarn                                                                             Comparative                                              poor  in strength                                                                            is brittle                                                                             sample                                                         and in                                                                         elongation                                       307  2.5  0.435                                                                               4.35 45  somewhat                                                                             somewhat poor                                                                          dried yarn                                                                             Present                                                  poor  in strength                                                                            is brittle                                                                             invention                                                      and in                                                                         elongation                                       308  3    0.432                                                                               2.31 45  good                  Present                                                                        invention                        309  4    0.411                                                                               2.08 43  good                  Present                                                                        invention                        310  5    0.403                                                                               2.11 45  good                  Present                                                                        invention                        311  6    0.387                                                                               2.14 39  good                  Present                                                                        invention                        312  7    0.374                                                                               2.31 39  good                  Present                                                                        invention                        313  8    0.351                                                                               2.05 37  good                  Present                                                                        invention                        314  9    0.330                                                                               1.88 35  good          yarn breakage                                                                          Comparative                                                            occurs often                                                                           sample                                                                 during spinning                          315  10   0.289                                                                               1.74 31  good          yarn breakage                                                                          Comparative                                                            occurs often                                                                           sample                                                                 during spinning                          __________________________________________________________________________

EXAMPLE 26

The same spinning solutions A and B as described in Example 25 were extruded from a spinneret in a conjugate ratio of component A:component B of 5:5 and in a side-by-side relation into a coagulation bath consisting of a 65% DMF aqueous solution kept at 15° C. The extruded filaments were subjected to a primary drawing to draw the filaments to 5 times their original length, washed with water and then dried at a drying temperature shown in the following Table 24 until the water content of the filaments was decreased to not more than 0.7%. The dried filaments were subjected to a secondary drawing and the successive after-treatments under the same conditions as described in Example 22 to obtain 3-denier composite fibers having a latent crimpability. Properties of the fibers are shown in Table 24.

                                      TABLE 24                                     __________________________________________________________________________                         Fiber property                                             Drying    Void      Water                                                      Experi-                                                                             tempera-  Surface                                                                             absorp-                                                    ment ture Porosity                                                                            area tion                                                                               Dye-                                                   number                                                                              (°C.)                                                                        (cm.sup.3 /g)                                                                       (m.sup.2 /g)                                                                        (%) ability                                                                              Others    Remarks                                __________________________________________________________________________                                   fiber is whitened                                316   60  0.609                                                                               17.1 56  poor  and yarn property                                                                        Comparative                                                          is poor   sample                                                               fiber is whitened                                317   80  0.537                                                                               16.3 50  poor  and yarn property                                                                        Comparative                                                          is poor   sample                                 318  100  0.411                                                                               6.55 43  somewhat        Present                                                        poor            invention                              319  120  0.403                                                                               2.11 45  good            Present                                                                        invention                              320  140  0.389                                                                               1.74 42  good            Present                                                                        invention                              321  160  0.381                                                                               1.57 41  good            Present                                                                        invention                              322  180  0.368                                                                               1.35 39  good            Present                                                                        invention                              323  190  0.346                                                                               1.38 37  good  fiber is colored                                                                         Comparative                                                          and becomes brittle                                                                      sample                                 324  200  0.312                                                                               1.19 35  somewhat                                                                             fiber is colored                                                                         Comparative                                                    poor  and becomes brittle                                                                      sample                                 __________________________________________________________________________

EXAMPLE 27

The same water-washed filament tows as those obtained in Example 26, which had been swollen with water, were dried by means of a hot roller type drier kept at 120° C. until the water content of the tows was decreased to various water contents shown in the following Table 25, and the dried tows were treated under the same after-treatment conditions as described in Example 26 to obtain 3-denier composite fibers having a latent crimpability. Properties of the fibers are shown in Table 25.

                                      TABLE 25                                     __________________________________________________________________________                        Fiber property                                                       Void      Water                                                       Experi-                                                                             Water    Surface                                                                             absorp-                                                     ment content                                                                            Porosity                                                                            area tion                                                                               Dye-                                                    number                                                                              (%) (cm.sup.3 /g)                                                                       (m.sup.2 /g)                                                                        (%) ability                                                                            Others     Remarks                                  __________________________________________________________________________     325  0.1 0.381                                                                               1.74 39  good           Present                                                                        invention                                326  0.3 0.379                                                                               1.83 40  good           Present                                                                        invention                                327  0.5 0.402                                                                               2.09 43  good           Present                                                                        invention                                328  0.7 0.411                                                                               2.13 44  good           Present                                                                        invention                                329  0.9 0.424                                                                               2.17 45  good           Present                                                                        invention                                330  1.0 0.426                                                                               2.16 45  good           Present                                                                        invention                                331  1.5 0.473                                                                               9.31 50  uneven                                                                             uneven in fineness                                                                        Comparative                                                         and in yarn property                                                                      sample                                   332  2.0 0.518                                                                               16.3 53  uneven                                                                             uneven in fineness                                                                        Comparative                                                         and in yarn property                                                                      sample                                   333  5.0 0.780                                                                               20.5 71  uneven                                                                             uneven in fineness                                                                        Comparative                                                         and in yarn property                                                                      sample                                   __________________________________________________________________________

EXAMPLE 28

A polymer component A consisting of 80 parts of an acrylic polymer, which had a composition of AN:MA:SMAS=90.5:9.0:0.5(%), 20 parts of cellulose acetate and 10 parts of an acrylic copolymer, which consisted of AN and a comonomer represented by the formula of CH₂ ═C(R₁)--COO--CH₂ CH₂ O)_(l) (CH₂ CH(CH₃)O)_(m) R₂ (R₁, R₂, l and m are shown in the following Table 26) in a weight ratio of AN:the comonomer of 90:10, and a polymer component B consisting of 90 parts of an acrylic polymer, which had a composition of AN:MA:SMAS=87.5:12.0:0.5(%), 10 parts of cellulose acetate and 5 parts of the above described acrylic copolymer consisting of AN and the comonomer in the same composition ratio as described above were separately dissolved in DMF to prepare spinning solutions A and B containing 25% of the polymer components A and B, respectively. The spinning solutions A and B were extruded from a spinneret in a conjugate ratio (weight ratio) of component A:component B of 5:5 and in a side-by-side relation into a coagulation bath consisting of a 65% DMF aqueous solution kept at 20° C. The extruded filaments were subjected to a primary drawing to draw the filaments to 5 times their original length, and the primarily drawn filaments were washed with water and then dried until the water content of the filaments was decreased to 0.5% by means of a hot roller type drier kept at 110° C., while blowing hot air kept at 130° C. Then, the above dried filaments were subjected to a secondary drawing to draw the filaments to 1.3 times their original length. Further, in order to improve the crimpability of the filaments, the secondarily drawn filaments were subjected to a primary shrinking at 130° C. under wet heat to shrink the filaments to 0.9 times their original length, the primarily shrunk filaments were subjected to a tertiary drawing at 170° C. under dry heat to draw the filaments to 1.4 times their original length and further the drawn filaments were subjected to a secondary shrinking at 140° C. under dry heat to shrink the filaments to 0.9 times their original length. The thus treated filaments were mechanically crimped, and the crimps were set to obtain 3-denier composite fibers having a latent crimpability. When the fibers were treated with boiling water kept at 100° C. for 5 minutes, crimps were able to be easily developed in the fibers. The following Table 26 shows the states of void and fiber properties, before and after crimps are developed, of the composite fibers obtained by varying R₁, R₂, l and m of the comonomer in the acrylic copolymer. It can be seen from Table 26 that all the above obtained composite fibers have excellent fiber property and water absorption.

                                      TABLE 26                                     __________________________________________________________________________                                       After Crimping                                             Before Crimping             Fiber property                                             Fiber property         Crimp property                                          Wa-                 Wa-         Elas-                                  Void    ter         Void    ter     Per-                                                                               tic Residual             Exper-                                                                             Comonomer Poros-                                                                             Sur-                                                                               ab-     Elon-                                                                              Poros-                                                                             Sur-                                                                               ab-                                                                               Number                                                                              cent-                                                                              recov-                                                                             per-                 iment                                                                              in acrylic                                                                               ity face                                                                               sorp-   ga- ity face                                                                               sorp-                                                                             of   age ery                                                                                centage              num-                                                                               copolymer (cm.sup.3 /                                                                        area                                                                               tion                                                                              Strength                                                                            tion                                                                               (cm.sup.3 /                                                                        area                                                                               tion                                                                              crimps/                                                                             crimp                                                                              crimp                                                                              crimp                ber R.sub.1                                                                           R.sub.2                                                                           l m g)  (m.sup.2 /g)                                                                       (%)                                                                               (g/d)                                                                               (%) g)  (m.sup.2 /g)                                                                       (%)                                                                               inch (%) (%) (%)                  __________________________________________________________________________     334 H  H   0                                                                                0                                                                               0.351                                                                              1.98                                                                               37 3.1  39  0.355                                                                              2.13                                                                               36 50   52  56  29                   335 H  H  10                                                                                0                                                                               0.338                                                                              1.83                                                                               35 3.2  41  0.341                                                                              2.07                                                                               36 51   55  55  30                   336 H  H  10                                                                               10                                                                               0.335                                                                              2.01                                                                               35 3.0  40  0.339                                                                              2.15                                                                               35 48   50  66  33                   337 CH.sub.3                                                                          H  15                                                                               10                                                                               0.364                                                                              2.15                                                                               39 3.2  38  0.368                                                                              2.19                                                                               38 53   57  62  35                   338 CH.sub.3                                                                          CH.sub.3                                                                          15                                                                               20                                                                               0.657                                                                              2.07                                                                               37 3.1  39  0.362                                                                              2.24                                                                               30 55   59  63  37                   __________________________________________________________________________ 

What is claimed is:
 1. Porous acrylic synthetic fibers consisting of 2 to 30% by weight of cellulose acetate and 70 to 98% by weight of an acrylic polymer, the cellulose acetate being distributed in the acrylic polymer in an elongated form with the longest dimension thereof being parallel to the fiber axis, said synthetic fibers having substantially no microvoids, but having mainly macrovoids therein, and having a surface area A of voids of no greater than 15 m² /g, a porosity V of 0.05 to 0.75 cm³ /g, and a V/A ratio of not less than 1/30.
 2. The fibers as claimed in claim 1, wherein the acrylic polymer contains at least 80% by weight of acrylonitrile.
 3. The fibers as claimed in claim 2, wherein the acrylic polymer contains 85 to 93% by weight of acrylonitrile.
 4. The fibers as claimed in claim 1, wherein the acrylic polymer contains an acrylic copolymer containing 5 to 30% by weight of a monomer having the general formula ##STR108## wherein X is R₂ or ##STR109## R₁ and R₃ are H or CH₃, R₂ is H, NH₄ or an alkali metal, and l and m are integers of from 0 to 50 such that O<l+m≦50, said acrylic copolymer being no greater than about 33% by weight based on the total acrylic polymer content of the acrylic synthetic fibers.
 5. The fibers as claimed in claim 1, claim 2, claim 3 or claim 4, wherein said fibers have voids formed by phase separation of the acrylic polymer and cellulose acetate.
 6. The fibers as claimed in claim 1, claim 2, claim 3 or claim 4, wherein the amount of cellulose acetate is 3 to 25% by weight.
 7. The fibers as claimed in claim 6, wherein the amount cellulose acetate is from more than 10% by weight to 18% by weight.
 8. The fibers as claimed in claim 1, claim 2 or claim 3, wherein the acrylic polymer contains 0.3 to 1.5% by weight of a copolymerizable monomer containing a sulfonic acid group.
 9. The fibers as claimed in claim 8, wherein the amount of the copolymerizable monomer is 0.5 to 1.2% by weight.
 10. The fibers as claimed in claim 8 or 9, wherein the copolymerizable monomer is sodium methallylsulfonate or sodium allylsulfonate.
 11. The fibers as claimed in claim 1, wherein the content of microvoids in the porosity of the fibers is not greater than 30% by volume, said microvoids being voids having diameters of 2,000 Angstroms or less.
 12. The fibers as claimed in claim 1, wherein the surface area A of the voids is from 0.02 to 10 m² /g.
 13. The fibers as claimed in claim 1, wherein the porosity V is from 0.05 to 0.60 cm³ /g.
 14. The fibers as claimed in claim 1, wherein V/A is 1/20 or more.
 15. A porous acrylic synthetic fiber consisting essentially of a blend of from 2 to 30% by weight of cellulose acetate and from 70 to 98% by weight of an acrylic polymer, said cellulose acetate having an acetic acid content of from 48 to 63% and an average polymerization degree of from 50 to 300, said acrylic polymer containing at least 80% by weight of acrylonitrile, from 0.3 to 1.5% by weight of allylsulfonic acid, methylallylsulfonic acid or salt thereof and the balance is monomer copolymerizable with acrylonitrile, said cellulose acetate being present in the form of elongated rods distributed in a matrix of said acrylic polymer so that the cellulose acetate rods are present in the fiber wall and in the interior of the cross section of the fiber, the longest dimension of said cellulose acetate rods extending parallel to the fiber axis and the ratio of length to diameter of said cellulose acetate rods being 10 or more, said cellulose acetate rods having voids at the circumferences thereof and in the interior thereof caused by phase separation of said cellulose acetate and said acrylic polymer, said voids consisting of not greater than 30% by volume of voids having a diameter of less than 2000 Angstroms and the remainder of said voids having a diameter of 2000 Angstroms or more, said fiber having a surface area A of said voids of not greater than 15 m² /g, a porosity V of from 0.05 to 0.75 cm³ /g, and V/A being not less than 1/30.
 16. A porous, acrylic, synthetic resin fiber, in which the polymeric component of said fiber consists of a mixture of(A) from 2 to 30% by weight of cellulose acetate, and (B) from 70 to 98% by weight of a polymer material selected from the group consisting of1. acrylic polymer consisting of from (i) at least 80% by weight of acrylonitrile, and (ii) less than 20% by weight of monomer or monomers copolymerizable with acrylonitrile; and
 2. mixture of said acylic polymer and an acrylic copolymer consisting of (i) from 5 to 30% by weight of monomer having the formula ##STR110## wherein R₁ is H or CH₃, X is selected from the group consisting of H, NH₄, alkali metal and ##STR111## wherein R₃ is H or CH₃, and l and m are integers of from 0 to 50 and 0<l+m≦50, (ii) at least 70% by weight of acrylonitrile and (iii) the balance is said copolymerizable monomer, with the proviso that the amount of said acrylic copolymer is not greater than 33% by weight, based on the total weight of said polymeric component of said fiber,said fiber having a surface area A of voids of not greater than 15 m² /g, a porosity V of from 0.05 to 0.75 cm³ /g and the ratio of ##EQU2## being 1/30 or more, said cellulose acetate being distributed in said acrylic polymer in the form of elongated rods having the longest dimension parallel to the fiber axis, said fiber having mainly macrovoids formed by phase separation of said cellulose acetate and said acrylic polymer.
 17. The fiber as claimed in claim 16 in which said polymer material (B) consists of said acrylic polymer.
 18. The fiber as claimed in claim 16 in which said polymer material (B) consists of said mixture of said acrylic polymer and said acrylic copolymer.
 19. The fiber as claimed in claim 16, claim 17 or claim 18, containing from 3 to 25% by weight of cellulose acetate.
 20. The fiber as claimed in claim 16, claim 17 or claim 18, containing from more than 10 to 18% by weight of cellulose acetate.
 21. The fiber as claimed in claim 16, claim 17 or claim 18, in which said acrylic polymer contains from 85 to 93% by weight of acrylonitrile.
 22. The fiber as claimed in claim 16, claim 17 or claim 18, in which said acrylic polymer contains from 0.3 to 1.5% by weight of a copolymerizable monomer containing a sulfonic acid group.
 23. The fiber as claimed in claim 22 in which said copolymerizable monomer is sodium methallysulfonate or sodium allyl sulfonate.
 24. The fiber as claimed in claim 21 in which said acrylic polymer contains from 0.5 to 1.2% by weight of a copolymerizable monomer selected from the group consisting of sodium methallylsulfonate and sodium allyl sulfonate.
 25. The fiber as claimed in claim 16, claim 17 or claim 18, in which the content of microvoids having diameters of 2000 Angstroms or less is not greater than 30% by volume, based on the total volume of voids in the fiber.
 26. The fiber as claimed in claim 16, claim 17 or claim 18, in which the surface area of the voids is from 0.02 to 10 m² /g.
 27. The fiber as claimed in claim 26, in which the porosity V is from 0.05 to 0.60 cm³ /g.
 28. The fiber as claimed in claim 27 in which V/A is 1/20 or more.
 29. The fiber as claimed in claim 16, claim 17 or claim 18 in which the celluloe acetate is present on the fiber wall and in the interior portion of the fiber so that intercommunicating macrovoids are present on the fiber wall and in the interior portion of the fibers.
 30. The fiber as claimed in claim 29 in which at least 70 volume % of the voids in the fiber are macrovoids having a diameter of greater than 2000 Angstroms.
 31. The fiber as claimed in claim 16, claim 17 or claim 18 in which said monomer or monomers copolymerizable with acrylonitrile are selected from the group consisting of alkyl acrylates, alkyl methacrylates, acrylamides, methacrylamides, vinyl acetate and sulfonic acid group-containing monomers and salts thereof. 